ML040330241
| ML040330241 | |
| Person / Time | |
|---|---|
| Site: | Perry  |
| Issue date: | 01/26/2004 |
| From: | Root E FirstEnergy Nuclear Operating Co |
| To: | Underwood M Office of Nuclear Reactor Regulation, State of OH, Environmental Protection Agency |
| References | |
| PY-CEI/OEPA-0412L | |
| Download: ML040330241 (116) | |
Text
FENO C O
nrS!W8MXW 70170 Perry Nuclear Power Plant 10 Center Road Perry, Ohio 44081 Edward M. Root Manager - Radwaste, Environmental, Chemnistry 440-280-5646 Fax: 440-280-5681 January 26, 2004 PY-CEIIOEPA-0412L Ohio Environmental Protection Agency Northeast District Office Attention: Ms. Marie Underwood 2110 E. Aurora Road Twinsburg, OH 44087-1969 Ladies and Gentlemen, This letter is to document the request of Perry Nuclear Power Plant (PNPP) staff to determine if it is allowable to perform interference removal for chlorine analysis using the HACH Pocket Colorimeter. On January 20,2004, Mr. Leo Harte of PNPP spoke with Ms. Marie Underwood of the Ohio Environmental Protection Agency (OEPA) concerning the HACH analysis and the use of interference removal methods stated in HACH documents. Per the direction of Ms. Underwood, Mr. Harte also spoke with Mr. Eric Nygaard of the OEPA. The HACH Pocket Colorimeter Instruction Manual and the HACH Technical Information Series - Booklet No. 17 were sent electronically per the OEPA request. A hardcopy of each document is enclosed.
If you have any questions or require additional information, please contact Mr. Leo Harte at (440) 280-5514.
Attachments cc:
OEPA Columbus Office NRC Region III NRC Resident Inspector NRC Project Manager NRC Document Control Desk (Docket No. 50-440)
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- 9/19/2003 T+/-res 11,48 AM Toe Jusin-Peat 0 914402805681 Pa99s 002.035 Current Technology of Chlorine Analysis for Water and Wastewater Technica! Information Series -Booklet No.17 By Danial L Harp Ul. no. 7019 L21.5 Printed in U.S.A.
CHach Company. 2002. All rights are reserved.
.3
/19/2003 Tim.a 11t49 AM Tos Juuth._P4at 0 9.144028O56BP Pagel 003-03S In memory of Clifford C. Hach (1919-1990) -
inventor, mentor, leader and, foremost, dedicated chemist
. 9/19/2003 Tme# 11t48 AM Too Justn-Peat 9,14402805681 Pags 004-03s Current Techno!cgy of Chlorine Analysis for Water and Wtstewater Table of Contents Paoe
- 1.
Overview ot Chlorine Chemistry in Water Trearnent.1
- 2. Analytical Methods fo r
Chlorine and Choramines
.2
- a. DPD Colorimnetrkc Method....
- b. DPD Ttration Method.............................
5
- c. Iodometric Titration Method.
- d. Amperometric Tltration Methods.
6 e: OtherAnalytical Methods:
Orthotolidine..
Syringaldazine (FACTS)..............
...... 9 ElectIrode
- 3. Method Interterences and Sources of Enors........
- a. Sampling Considerarions 1
- b. Interferences Common to All Chlorine Methods.
11 Other Disinfectants..............................
.1....
1 Manganesc Compounds..............................
12 Organic Chlorarnines..............................
12 Bromides in Chlorinated Waters......................................
12
- c. Errors Corron to Total Chlorine Determination.s.......................................
12
- d. Interterences in the DPD Methods
.3.................
3 Calibration Non-Linearity 13 Precautions in Using Permanganate as an Equivalent Standard.
13 Monochlorarnine Interterence in the Free Chlorine Test............................................
15 Stability ot the Colored Reaction Product.............................................
16 Compensation for Sample Color and Turbidity.
16
- e. Interferences in the Amperometric Titration Methods 17 Deposition on Electrode Srfaces 17 Manganese Interference...............
17 Nitrite Interference.......................................
17 Cheoice ot Reductanr 19 Effect of Iodine Demand on End Point Determinations 19 Order of Reagent Addition
.20
- 4. Method Comparisons ad Pertormance Evaluations..
21
- a. Field Kit or Laboratory Comparisons -------------------......
21
- b. Performance Evaluations of Residual Chlorine Process Analyzers
- 5.
Selection of theAppropriateTesting System...................................
24
- a. Fileld Testing....
24 b
- r.
Laboratory Testing...........
5...............
25
- c. On-line Automated Testing 26
- 6. Conclu sion.s..........
27 References
.... 29 Ac n..ow.ed.gen.nts 30
i9/19/2003 Times 11s46 A~M Too.tujotin_.oat
- 9.14402805681 a,0O-3 Pages 005-o35
- 1. Overview of Chlorine Chemisby in Water Treatment Chlorination of public water supplies hs been practiced for almost 1(X) years in the United States. Altlhougl the prrs anid coIns of dLisinfection witl clforine lave been exteasively debated, it remains te most widely used chemical for disinfection of water in the US.
Gomrelensive information cxplaining clorine chemistry in water treatment is available in several excelleit references describing cl-dorination and disinfection practices. (See Ref: 1.1 - 1.4). An overview emphasizing general chemistry of cllorine disinfcction will he presented lere.
Chlorine usually is added to water as the gaseous form or as sodium or calcium lypolclorite. Chlorine gas rapidly lydrolyzes to iypochlorous acid according to the following equation:
C 11
+
2 0 -HOC
+ H' + Cl-Similarly aqueous solutions of sodium or calcium lypoclilorite will hydrolyze according to:
Ca(OC) 2 + 2H20 Ca + 2HOCI +20H-NaO
+ i0 Na + HOCI + OH TMe two cheical species formed by cllorine in %water hvpuclilorous acid (HOCi) and lypocilorite ion (OC-),
are commonly referred to as "free available chlorine.
Hypochllorous acid is a wealc add ad will disassociate
- ccording to:
HOCI H- + OCt In waters with pH between 6.5 and 8.5, the reaction is inicomplete and both species (HOCI and OCI-) will be present. Hypodlorous acid is the more gernicidal of the two.
A relatively strong oxidizing agent, chlorine can react with a wide variety of compounds. Of particular irrortance in disinfection is the chlorine reaction witl nitrogenous compounds-sucI as ammonia, nitrites and amino acids.
Ammonia, commonly present in natural waters, will react witl hlypochilomus acid or lypoiorite ion to form monocllloranine, dilchloramine and tricliloramine, depending on several fictors such as pH and temjxrature. Typical ractions follow.
NH, + HOCI -- NH2C1 (rmonochlorarrine)+ H-2O NH2CI HOCI -NHCI 2 (dichlorarrine)+ H20 NHCI 2 + HOCI Nd, (trichloarrine) + H2O Known as "break-point" reactios, they are irpxrtant in water disinfection. The diloranines are potent biocides but not as effective as hypocllomus acid or the lhypocllorite ion.
0 0
In0 co I
CO.UPiNED RESIrALI (MUAINLY MO.NOCHWAFAJUNE)
FREE CHLORINE RESIDUAL OF
>A Chlorine Dose Figure 1.1:Typical Break-point Chlorination Curve Chlorination of water to the extent that all ammonia is converted to either trichloramine or oxidized to nitrogen or other gases is referred to as 'brcak-point cllorination."
Figure L-1 slmws a typical brealc-poinlt cllorination curve. Prior to the break point, "combitned" clorine (monocllorarnie plus didloramine) predominates.
In disinfection systems in whic cllorarnination is practiced the goal is to remain at the peak of the curve prior to the break point. If the amount of unreacted ammonia is minimized, monocdiorarnie will be the predominant clloramine.
After the break point, free cdlorine (lyocllorous acid plus hiypocliorite) is the dominant dishifictant. 13pically the free chlorinc residual is adjusted to maintain a minimum level of 0.2 mgL C, througlout the distribution system The importance of break-point cllorination lies in the control of taste and odor and increased germicidal efidency. Thie killing power of clorine on the righlt side of the break point is 25 times lilgler than that of the left side (Re / 1). Hence, the presence of a fi= chlorine residual is an indicator of adequate disinfection. Thle shape of the break-point curve is very dependlent ol contact times water temperature, concentrations of ammonia and chlorine, and pH.
1
9/19/2003 Times 11s49 AM To JstiPsat
- 9,14402B0SGB1 a,0005 Pag0s 006-035 Tlne use of monochlorarnine as an alternate disilfectt for drinldng water has received attention lately due to conceni about the possible formation of cliforinated by-prducts when using free chlorine disinfection.
Considerable debate continues about the merits of dclor-irniation disinfection. The reader is referred to Whitc's liandbook (Rf.L) for an ainimated discussion of the pirs and cons of chloramination practices in driuing water.treatunnt.
hi chlorarrination disinfection, moxnodloraminc is formed froin the reaction of anhydrous ammonia ad hypohllorous acid. In general, arnmoia is added fir-st to avoid formation of dlorinated orgnic comxoounds, which can exhibit objectionable taste and odlors. Bach offers a netlhod specific for inorganic monochiloramine dsinsfectant in te presence of organic chloramines (2?ef 1.2).
Thnroughout the U.S. Today, wastewatr effluents are chlorinated to Idl pathogens and theni dechlorinated bdfore discarge. iis corniloni practice resultcd frm several conprehensivc studies (Ref 1.5) which quantified the toxicity of dlorinated effluents on aquatic life. The amount of total residual chlorinc i the final cffluernt is regulated by a National Pollutart Discarge Elimiiation System (NPDES) permit. ¶Ipical permit limits for total residual chlorinie (RC) in the final effluent range from 0.(X)2 to 0.050 milligram per liter (rng/L). To the dlorination-dedllorination practitioner, this level translates to zero mg/LTRC.
Dechlorination by sulfur dioxide (SO2 ) is the most common process to meet zeroTRC effluent limits.
Sxdium bisulfite and sodium setabisulfite also have been used for chemical declilorination. In the dechlorination process using SO,, sulfurous acid is formed first:
SO2 + H2 0
- H2S03 Sulfumous acid te reacts with the various chlorine residual species:
H2SO + HCI-H + H2S04 kSO, + NH 2 CI + H20-NH4 CI + H2S 4 2-lSO, + NHCI2 + 2H20 - NHaI + HC1 + 2-ISO, 31-ISOJ, + NCd + 3H20 - NH4 a + 2HCI + 3H2S04 It is coImon practice to overdose the sulfur dioxide to intain a level up to 5 mng/L SO, in the effluent. This ensures the reduction of all chlorine residual species.
2 Analytical Methods for Chlorine and Chloramines 2a. DPD Colorimetric Method TIC DPD (N. Ndictlyl-pl-peylenlediarniine) method for residual chlorine wvs fist introduced by Palin in 1957 (Ref2l). Over the years it h-as become the most widely used metlod for determiiing frce and total cllorine in water and vastewater. Hach Company introduced its first dlorine test ldt based on the DPD chemistry in 1973.
ie c.hemical basis for the DPID chlorine reaction is
- lepicted in Figure 2.1. The DP) anue is oxidized by chlorine to two oxid-ation products. Ai a near neutral pH, the primary oxidation prAluct is a semi-quinoid cationic compound Inown as a urster dye. This relatively stable free raclical species accounts for the magenta color in the DPD colorimetric test. DPD can be further oxidized to a relatively unstable, colorless inine comotund. When DPD reacts with small amounts of chlorine at a near neutral pH, theUirster dye is the principal oxidation product. At higher oxidant levels, the formation of the utstable colorless imine is favored -
resulting in apparent "fading" f the colored solutioni.
H H
N 11 N.
Et H Et N-cl,*
E H
H
+
I N.
Et Et AMINE WURSTER DYE (colorless)
(colored)
Figure 2.1: DPD-Chlorine Reaction Products IMINE (Colodess)
The DPD Wurster dye color has been measured plotometrically at wavelengtis ranging from 49() to 555 nanometers (rim). The absorption spectum (Figure 2.2) hidicates a doublet peak witl maxima at 512 and 553 nm.
Fbr maximum sensitivity absorption measurements can be nmare re-reen 510 and 515 nnL Hah Cozxuiy has selected 530 nm as the measuring wavelengti for most of its DPD systems. Tis saddle between the peaks milimizes any variation i wavelength accuracy between instruments and extends the woring range of tlc test on some instrumn-xts.
2
sa 9/19/2003 Tima: 11%48 AM Tot JustinPeat 0 9.14402805601 Pa941 007-035 I
I I
I I I
7 7 '
I 0.2500 0C.)
Cco
-2 U0) 0.1,500 0.0500 400o.0 440.00 480.00 520.00 560.00 600.00 Wavelength, nanometers Figure 2.2: Absorption Spectrum - DPD Wurster Compound Moncihloramine and dicdlorernin are slow to tect directly with DPID at a near neutral pE To quantify tlcse speciec, the test is performed under bligltly acidic conditicns in the presence of iodide ion. The iodide reacts with the chloraiines to form iodine as the triodide ion (i-):
NH 2Cl + 31-+ H2O H+-
NHOH Cr + 1-NHCI 2+ 31- + H 20 + 2H NH40H 2C1 + 13-The trilodide, in turn, reacts witlh DPD, forming the Wdirster oxidation product. Th1,ere is very little conlirmcd evidlence that tridcloramine species can be quantified wlhen using iodide with DPD (Ref 22.
In practice, only a trace of iodide is required at pH 6.2-
- 6. 5 to resolve monoclhloranine. Skmdad Met bod. 1for the Exznnination of Water and Wlstezxer (Ref 2 3 stipulates the addition of approximately 0.1 mg of potassium iodide to a I 0mi sample to determine mronocdloraminc. By adding excess potassium iodide (an additional 0.1 gram or more per 10-mL sample),
dichloramine is included It is not entirely clear at what level of iodide the didlilorarine frlaction begins to intrude into the monoclloramine results.
Two "standard" DPID colorimetric metlhods generally are recognized in the international community. These are tlhe Stcmdnl Metbx)od, 4500-Cl G and International Organization for Standarclization (ISO) Mcthod 7393/2 (Ref 2.4). Thle ISO metlhod las been adopted by most of the members of the Euopean Union. Germany's DN Standard 38 408 G4 for free and total chlorine is modeled after ISO 7393/2. Table 2.1 shows the main differences between Standard Metlhods 450002 G and ISO 7393/2.
Both.Stlalat MethJod and ISO procedures call for liquid DPID reagents prepared from DPD sulfate or DPD oxalatc salts. Liquid DPD reagents, inlherntly unstable, are subject to oxidation firom either atmospleric oxygen or dissolved oxygen present hI the preparation water It las bee, slown tlhat the oxidation of DPID by oxygen is pHn-depenrent (Rc7e25). The liquid DPD formulations attempt to retard oxidation by lowering the pH of the indicator regr-nt.
Mhe liquld formulations also incorporate disodium cthylaeecniamine tetcaacetate (Na2EDTA) in ordcer to
'retard deterioration due to oxidation and, in the test itselg provide suppression of dissolved oxygen errors by preventing trace metal catalysis" (Ref2(6. Tie practice of adding NaEDYTA to the DPD indicator reagent is questionable because of the low solubility of EDTA in dilute acid solutions.
Stan datrd ebJaod; and ISO procedures botlh use plhosplhate buffers to adjust the sample pE to between 6.2 and 6.5. The slightly acidic pH is pre-frred to quantitatively resolve the clhiorarrine species and to niinimize interferences. Phosplhatc bufErs, h-owever, do not work in lard or brackish waters. Calcium and magnesium ions in the sample will precipitate the phosplhate and destroy the buffering capacity (Ref2 7).
Because aqueous plhosplhte solutions are excellent growtl media for biological growtl, highly toxic mercuric dloride is added to prsrve -die reagent.
3
is 9/19/2003 Tims 11t49 AM Too JustnPsoat 914402805681 P11,76 008-035 Test Range Apparatus Reagents Calibration Standard Methods 0.01 - 4 mg/L as chlorine Spectrophotometer: 515 nm Filter Photometer 490 - 530 nm ISO 7393/2 0.03 - 5 mg/L as chlorne Spectrophotometer: 515 nm Discontinuous wavelength close to 510 nm Comparator with glass color standards DPD sulfate or DPD oxalate DPD sulate (Final SM and ISO formulations are equivalent)
(Both SM and ISO state combined powder formulations are acceptable)
Permanganate dilutions: 515 nm Procedure Correction for Mn7+
1 0-mL sample to 0.5 mL each reagent (or increase volumes proportionally)
TRC: ab. 0.2 gm U /1O-rnL sample arsenite + buffer to sample, then DPD expressed as mg/L chbrine Iodine dilutions generated from iodate+ acid pH adjusted prior to additions of mixed reagent 100-mL sample added to 5.0 mL each reagent TRC: ab. 1 gm Kl /100 mL arsenite to sample, then add to DPD + buffer expressed as mrnmoles/L chlorine Reporting Table 2.1: Differences Between Standard Methods 4500-Cl G and ISO 739312 Eacli Compaly DPD powder formulations overcome the dlsadvantages of using liquid reagents. nie DPD indicator and buffer are corrbined in powder form, minimizing degradation by oxidation and microbial action. Because Haldis DPD powder hidicator docs not exist in an ionized state, it i not subject to air oxidation as is the liquid DPD reagent. Haci's combined DPD reagents also incorporate EDT to prevent metal-catalyzed oxidation.
Kiclis buffer component rmalkes use of a carboxylate-.
phiospihate system whicih wors extremely well in iigh hrdhess and bracldsl water samples.Up to 1000 mglL iCiO lardness can b tolerated witi eitier the free or total clhlorine powder formulations. Mercuric salts are not used in any of Eaci Company DPD formulations.
Eacl Company's DPD powder reagents are quite stable wlen protected from moisture, liglt and temperature extrecmes. Excllent reagent stability is acieved by sealing the reagent in unit-do.sc foil poucies. AccuVac' DPD reagent ampuls are air-evacuated mid hence are protected frot oxidation and moisture. It is recommended that aU DPD reagents, both liquids and powders, be stored between 10 to 25 C (50 to 77" F-)
for greatest stability.
Eci Comp-anly las produced a stable liquid DPD reagent. TMe DPD Indicator Solution for Ultra Low Rangc (ULIR) Cilorine, Cat. No. 24932, is sealed in a unit-dose arnpule under argon gas. Tle use for this reagent is in trace determiations of total chlorine in water and wastewaters. liquid reagents are preferred for trace levels of chlorine - Iess than 20 micrograms per liter (pg/L).
Powdered reagents typically leave a very sull 4
undissolved residue wlen added to the water sample.
Altlougl the resulting turbidity is not evident visually, it may be sufficient to interfere i trace colorimetric measurements. Shelf studies indicate the UIR-DPD reagent exhibits no loss in sensitivity to cllorine over a one-year period Re2).
For trace determinations of cltlorine, purity of the buffer and iodide components are critical. Orpnic buffer impurities can exhibit a"cllorine demand" wlen added to a sample containing trace amounts of chlorine. As statcd previously, phlosphare buffers generaly are useeiss in samples containiing hardcss. Liquid plosplate buffers c-an contain insoluble impurities or microbiological growti whicl may cause turbidity when added to the sample. Iodide often contains iocline o-iodate impurities whiclh react directly witi the DPD indicator. Exposure to oxygen and light will gradualiy oxidize iodide to trfiodide even in the solid state.
A stable liquid buffer/lodide reagent developed by Hacl is suitable for trace chlorine analysis. Tle ULJL Chlorine Buffcr, Cat. No. 24931, is specially treated to remove any cllorine demand from its components. lodide in the reagent is controlled to minimize oxidation impurities.
The UIR Chlorine Buffer is packaged under argon in a llght-protected, unit-dose ampule.
Another important consideration for trace analytical measurements is the "reagent blanle'nis i the amount of interference due to the addition of the reagents. In the DPD colorimetric test for chlorine, oxidation of the DPD indicator gives the same colored Witixster dye product as the reaction of indicator witl chlorine. Wilen the DPD reagent is added to the sample conaining chlorine, the
i 9/19/2003 Tima, 11t48 AM Too Justin_Peat 9.14402805681 Pagao 009-035 amount of color measured will be the sum of the reaction product or DPaYQJ and the added oxidized DPD. For trace analysis, tle reagent blanic contribution must be accurately lanlown.
Ideally, the amount of color due to the reagent addition can be detenmined by using a sample kiown to contain no oxidant. Unfortunately, a trIly "oxidant-fee" samp!e does not exist. [f a relatively strong redueing agent suci as sulfite or ferrous ammonium sulfate werc added to the sample, it would reverse any colored DPDurster dye present i the indicator reagent to the free amine, thereby preventing reagent blank compensation.
1ac Compuy has developed a procedure to determine the re-agent blank for the ULR-DPD mehod. The procedure decilorinates the sample witiout affecting the color contributed by te indicator reagent. In the reagent blank compensation procedr, a non-reducing agent is added to tle sample to remove free and combined chlorine. Next, indicator and buffer reagents are added to the dechlorinuted sample, following the normal test procedure. The resulting color is used to correct the sample analysis results. Conrsistent reagent blank values, equivalent to less tan 3PgfL cllorine, are obtained wlen using the ULR-DPD reagents.
Whlen using Haic Company's method for LR total chlorine testing, cilorine residuals as low as 2 pgL can be determied (Rf28,). Tiis level of detection was determined using the US. Environmental Protection Agency (U!SEPA) procedure for estimating the method detection limit (MDL) (Ref 2 9). ie upper range for the test is 500 pg/L as Cl2.
Monitoring uses for the ULR-DPD iniethod for total chlorine include decllorination of feedwvater to reverse osmosis membranes or ion-exclange resins, make-up water for the plarmaccutical and beverage Industries, aid in wastewater trcated to meet NPDES requirements.
The ULR-DPD metlod is USEPA-accepted for total chlorine determinations in driilnkg water and wastewaters.
H H
N N Et H I Et H
AMINE (colorless) 4.
H H N.-
4N-Etf Et WORSTER DYE (colored)
H H
N-
-I It IMINE (clourlsess)
I l
2Fe3 2Fe2 Figure 2.3: Chemistry ol DPD-FASTitration formulations as those specified in the referenced DPD colorimetric methods. Hence, the inlierent problems of reageit instability and bufferin3 of hard water samples cited above also are applicablc to the reference titration procedures.
The ferrous iron titrant reagent used in the Standard Metlods and ISO DPD titration methods is prepared mm ferrous ammonium sulfate. Tlis titrant solution is very unstable, susceptible to oxidation, and must be frequently standardized against standard potassium diclromate. The titrant geneally is used for only one montl.
Hach Company hias improved the ferrous titrant solution by using a primary staldard ferrous etlylenediammonium sulfate (Oespes reagent).salt under oxygenfiee conditions. The titrait is sealed in Digital Titrator cartridges after preparation to a 0.00564 N (normality) concentration using de-oxygenated water.
Wal. minimal exosure to oxygen due to the packaging, the Ferrous Ethylenediarnmonium Sulfate (FEAS)Tiltrant, Cat. N. 22923, exhibits excellent slelf stability (grcater than six months) compared to that of the reference method formulations.
In HaIcd; Coipany's DPD titration mcthod, a DPD Free or Total Clilorine Reaget Powder Pillow is added to 25 mL of samplec After iull development ofthe Wirsterdye,the reacted sample is titrated to the colorless end point using FEAS with the Digital Titrator. The number of digits required to the end point is divided by 00 to obtain the mg/L cllorine.
For most samples, there is no clear advantage to using tle DPD titration metlod over Haclis DPD colorimetric metlhocL In fact, there may be several disadvantages.
First, the titration procedure requires additional time to perform In the case of possible monoclloramine 5
2b. DM 1rtion Method The DPD titration metlhod is hosed on tlhe same chemistry as the DPD colorimetric method - in that DPD is oxidized by chlorietc (or iodine in the case of cllioramines) to te magenta-color species. Thc red color then s titratcd witi a ferrous reducing agent to the colorless end point. The reaction chemistry is depicted in Figure Z3.
Standard Methods and ISO DPI titration procedures botlh use the same buflcr and indicator reagent
911912003 Times 11%4B A~M T JUitiEPoa~t 6 914402805681 kae L-3 race#
u-035 intrusion into free chlorine (see Section 3d), the additional time required for a free cllorine titration mrdy lead to errors. Accurate measurement o smple volume for the titration is essential. To achieve accuracy, a pipet must be used - a procedure which can lead to loss of volatile chlorine species. Thie visual estitnation of tl e titration end point is inprecisc compared to the measurement of color obtained by using a colorimeter or spectroplhotometer 2c. Iodometric irLation Thc starch-iodide titration metlod, one of the oldest methods for determining chlorine, is very nonspcific for oxidants and generally is used for total chlorinc testing at levels above 1 mfL Cl,. The methllod is based on reaction with thiosuiffte solution:
Ci - 3KI -I F 3K
+
+ 2CI IJ + 2Na2S2O3 31 + 4Na + S4O,-
The end point of the titration is indicated by the disappearnce of the blue-colored, starclhodide complex.
Thc titration usually is peformed at a sample pH betwveen 3-4.
Research by Hatch and Yang (Ref 2 10) las shown sample temperatures above 20 °C can produce significant errors if starch is used as the titration end-poinit indicator Their studies indicate the release of triodick from the starch helix is temrerature-dependent. For maximum accuracy, iodometric titrations using starcl indicator should be performed at sample tenpratures less than 20 C (6.8 F).
A "back titration" is recommended for waters containing potential chemical interferences. In this case, a lnovwn amount of thiosulite is added in excess of the chlorine in the sample. Mle amounit of unreacted tiosulfate is titrated with a stiadard iodine solution. Tien, the total chlorine is calcuLated, based on the thlosulfate equivalency in the sample Tie chcmical reactions are:
Cl2 + 2S2O0 -
2CI- + S0,-
I + 2S 20,2 (excess) -
31 + S,0,2 Hach Company otfers several total chlorinc systems using tle iodometric titration method. lhically, tle aplication range is frm 1 to 70,000 mgL chlorinc Haci Company's iodornctric procedures are used to assay dilorine in comrnerdal blead solutions and in cllorinated wastewaters.
6 2d. Amperometric Titration Methods Amperometry is an electroclemical teclique that applies a small electrical voltage across two electrodes and measures the dnge in current resulting from chemical reactions taking place. Amperometric titration measures the current change as a function of titrant added. Typical ampermetric titration instrumentation indudes a probe or cell containuig dual platinum electrodes (biamperometric) or two dissimilar electrodes (for example, silver/platinum), a vnicroampere meter and a titrant-dispensation device.
In the amperometric deterimination of free cllorine, chlorine is titrated with a staxard reducing agent such as thiosulfate or plienylarsine oxide (PAO) at pH 7. A small potential is applied across the electndes before the titration begins. Current cannot flow between the electrodes unless two substances are present -
one that can be oxidized at the anode and another that can he reduced at the cathode. During the course of the titration, chloric is reduced at the catlode to chloride (Qr) from the reaction with PAO. PAO is oxidized frm the +3 to the +5 oxidation state at the anode:
PhAsO (PAO) + Cl2 + 2HO -
PhAsO(OH) 2 + 2Cr- + 2H' (Ph = phenyl)
As long as the oxidanit (free cllorine) is present in the titrated sample, a current flows througl the cell. When all of the oxicLit is reacted, the rate of current change is zero, signalling the end point of the titration. After the cld point is realcd, the solution cannot conduct current even though excess PAO is added. The amount of PAO used at the titration end point is proportional to the chlorine concentration in the sample.
In the case of cloramine determination, the pH is lowered to 4 and potassium iodide is added to convert the chloramine species to an e muvalent amount of triiodide ion:
NFHCI + 3- + H 2O +H
- NH 4OH + C- + 1,-
NHCI + 3r + H 20 + 2r-NH4 H + 2Ct +
The triiodide is titrated with PAO with tle current clange measured amperoerically:
PhAsO + I- + 2H20 31- + PhAsO(OH)2 + 2H' (Ph = phenyl)
a 9/19/2003 Time# 11.48 AM Tot Justun_Poat 9.14402805681 Paget 011-035 SrandanlMebodL; (Rf2.11) differentiutes between monochlloraunine and dichlioranine by performing the monochioramine titration in the presence of potassium iodide at pH. After titration, the pH is lowered to 4, additional iodide is added, and the titration is continued to resolve the diclhloramine fraction. Because an arnpermretric titration typically must be "over-shot" to determite the end point, the volume of titrint must be corrected for the over-shot increment. Tiis practice leads to some ambiguity in the deermination of monochloranilne and didclora.mine fractions, especially when present at low concentrations.
The direct amperomcntric titration of cllorinc or clloramines with a standard reducing agent is klowo as a "RvIrard" titration. Baclc titration with an amperometric end point also is used widely for the determination of total chlorine in water. The amperometric back titration is essentially the back iodometric titration method with an amperometric, rather tlan a visual, end-point detection.
The amperometric back titration method has been popular in wastewater laboratories for two reasons:
(1)The sample chlorine can be "fixed" at the sampling site with the addition of excess reducant.
(Z) Since the end point is reversed, there is less interference from iodinec-demand substances in the sample. The back amperonetric end point is signaled when free iodine (triiodide ion) is present -
as indicated by a current flow between the electrxles.
Amperometric titrations require a higher level of scill and care than the colorimnetric methiods for chlorine analysis.
Standa??! Metod; states the amperonetiric method "is the stuxindad of conmrarison for the determination of free or combined chlorine" (Ref212). However, the anperometric method Ls no longer accepted by ISO for the determination of chlorine species (Rf2 13). There is considcrable conflicting infornation about interferences with amperometric methods for chlorine in treated wvastewater and effluents (see Section 3e.).
Eah Company offers both forward and baclcward amperometric methodls for determination of fre and total chlorine in water Hach'sAutoCat 90XX)
Amnperometricmrator (Figure 2.4) is based on a biamperometric system that uses a dual platinum electrode (DP) probe. The AtoCat software controls the delivery of titrant from a glass burette driven by a step motor. The step motor requires 8.0O individual stepis to deliver the full 5.0 mL of titrant that it contails.
Tlis allos a volume resolution of 0.0(03 mL per step.
Figure 24: 1ach Company's AutoCAT 9000 AmperometricTitrator 7
of 9/29/2003 Times 11.48 AM Too Jumtin_Paat 914402BO561P Pages 012-03S A giass buret also may he used to dispense the titrant.
wDr.vbacl of using a buret include tl-Le fragility of the gasswvare and the relatively large dispensation. Even wien a tass A 5-mL buret is used, dispensation of one srll droplet of 0.(X)564 N PAO could relate to as muci as 20 Vg/ a2 i a forward titration using 2()0 mL
.of sanrrle.
Typical titration plots for Hacid'sAutnQt-9(X)O forward and bacic amierometric procedures are shown i Figures 2.5 and 2.6. lhe eid poiJt c;n be determined manually or automitically. In a manual endpoint cletermination, the analyst uses cursors to select a linear region on each side of the end point. Then the instunt calculates and places leas-squares regression line-, at eacl point. tlC intersection of the two best lines through the points is the end point. In an automatic end U~~~~~~V%:F point determInation, the instument searcles for a pair of intersecting lines that best it the titration curve. The end point is derived fim the intersection of the two points.
A comparison of currently available commercial amperometric systems shows lower detection levels ar possible with theAutoCAl 9000 because of micro.
dispensation and automatic determiination of the endpoint. Metiod detection limits fo. thC total chlorine forward titration are 0.0012 mg/L (1.2 Vg/L) a, and 0.(X)51 mgL (5.1 pg/L) for the back titration.
Hach Company's amperometric titration metiods meet the testing requirements for measuring diloriite according to the US. ttionai DikiidngWterAct Reglations as well as the NPDES compliance monitoring For a comprehensive review of analytical m-ethods which have been used to determine chlorine in water, the reader is referred to the Ameran Widter llhrf-n*
ANadtfion'; Dinfedtant RePidaMeasunwnent MetlxxI& (Ref 22). A review of oither metiods whicl have been commonly used in the water treatment industry follows.
2e. Other Common Analytical Methods Orthotolidine Method The ortliotolidine (CT) method for dlorine was first reported by Ellms and Hauser (Ref 214). The method has been modified several times to overcome stability problems and interferences related to monocliloramine brelahrough in the free dilorine procedure.
Tle orthotolidine metlod was dropped from the 14th edlition of St ancdaMef)cd, after the results of two round-robil studies (Reft 2.15, 216),ere released.
Both studies indicated the CT method gave poor accuracy and precision and a higl overall error in comparison with the other chlorine methods.
Two aquatic toxicity studies (Reft 217, 218) compared the DPID colorinetric, anrperometric titration and orthotolidinie methods for determining dlorine rcsiduals.
In both studies, the CT' method gave lower values at all concentrations of total dlorine relative to the other two methods.
Because of relatively poor accuracy and precision and a lack of specificity, the orthotolidine metlod generally is not accepted in the United States and most developed countries. Usage of this method Ls mainly confined to low-cost pool testuig applications..
Figure 2.5: Forward AmperometricTitration Plot Figure 2.6: Back AmperornetricTitration Plot 8
i 9/19/2003 Timeo 11,4 A ToI ustin_Poat 9.144020681a 3
PacVa1 013-03S Syringadazine CFACCS) Method This metiod is Txrsed ol tie rectiol of 3,5-dimethyl4 hydroxybenzzildazine (syringaldazine) with free dloinre on a 1:1 basis:
alternate procedure to rnove the chlorine demand by cilorinating the alcohol and dedliorinating by exsurc to sunlight or ultraviolet (U) liglt. Tlis procedure is not recommended, due to the flamrmbility of 2-propanol.
OCH3 H
OCH3
= N -NC
/
OH I
UCH 3
HOCI H
C C-N -
0 OCH3
+H30 + HCI The product is a redpurplc compound with naximum at 530 ln The publisled methoc knlown as the FACI metlhd (free avilable testing witl syringaldazine). The application reported as 0.1-10 mgfL a. The test has be.
the determination of total chlorine as well a oxidanits (Ref219).
The FAC1S method las been reported to be free cdlorine with little interferxce from m (44) ad monodioranie. A Standard Meth procedue (Ref2 20) for free chlorine deter is not recognized by the ISO.
Major disadvaltges of the FACrS method ar insolubility of the indicator and its productf intlicator solution, and a variable sensitivity t The syringaldazine indicator is prepared i 2 which it las limited solubiLity. It Is necessary leat and use ultrasoric agitation for several dissolve syruinldazine i the 2-proyxinol. Al propanol must be distilled to remove uniden impurities which exert a cllorine demand Had Corixny research shoWS a FACIS indu witI consistent sensitivity to chlorine is diffir produce, even with distillation of the 2-propa heat is excessive in preparation of the indica Cegrad;ation of the syringalda2ine can occur, decresed seinsitivity. Standard Methd; all o Although. not addressed in te Standad Methxods procedure, syringldazine idicator solutions cannot be stored i plastic containers. The solvent appariltly leacts out impurities in the rsin, resulting i a chlorine colorless demand i te indicator. For greatest stability, tle syrinpldazine reagent should be stored in an amber glass-stoppered botle protected from heat and UV light.
Another problem witl the FACMS procedure is fading of the oxidized (colored) species. This is due, in part, to the relative isolubility of the product when diluted by the red-purple aqueous sample. C3iswllU and O Halloran (Ref 221) reported the FACIS method is ulsuitable for free chlorine testing due to the instability of the oxidized reaction product. Increasing the propanol concentration did not significantly improve the solubility of the oxidation product. Also, the product decomposes rapidly
- a aIsorptn X
if the test pH falls out of the range of 65 to 6.8.
cl gel.aily is chlorille The StarmdMetxod procedure calls for a plosplate range is buffer to control the sample pH at 6.6. Hacli Company's
- n adapted to researcl has shown that sample liness at levels as low otlier as 200 mgfL CaCO, wll have an appreciable effect on the stability of the colored product. Precipitation of calcium phosphate destroys the buffer capacity with a resulting spec test pH lower tlr
). 5. At tis pH, color fiding is angese appreciable and color measurements must be made at od standardized intervals. A maleic-hydoxide buffer system is innations, it an nternative for lard water applications but does not worc well witl samples with higl allaiity.
r te Due to the difficulties of non-reproducible indicator torage of tle solutiots, inadequate buffer capacity with certain o chlorine.
samples, and color fiding, Haci Company does not offer
- -propan l, ~
a flee cllorine test based on the FACIS merlod to gentiy hours to Potentiometric Electrode Method so, the 2-The elecrode method is based on the potentiometric tificd measurement of free iodine produced when iodide is added to ami acidic sample containing an oxidait. The ator solution method is analogous to the iodornetric titration method ult tO iI that total oxidlant is measured and speciation of nol. Also if disinfectants residuals is not possible.
tor solution, resulting i ws an 9
t 9/19/2003 Times 11s48 AM To, Justin.Pyat 9,14402805681 paqat 014 @0Q S ie cic ctaxode is based on the Nernst equation:
E = E, + [2.303RT/2F log [lo IM]
where E =
measured potential E, =
standard potential 2.3 PT/2F =
Nernst corstant
[I] =
[r] =
iodine concentration iodide concentration In practice, a platinumiiodide electrode pair is used In combination with a millivolt (p1) meter. The iodide ion-sp~cific electrode (1.SE) serves as the reference electrode.
A <nrstnt excess of iodide (cr) is required in tle measured sample. ThisL is necessary to "fix"the concentration of triodide (1,) formed, so free iodine (1,)
can be measured It is important that the same amount of iodide is added to both calibration stanchids and the samp4le.
Tl* electrode method sufters from several interferelces.
Giloride ion can form the iodue-ciloride complex (12) wllch is not seLsed by the elctrodc. Organics in thie water sample can react with tle free iodine released durng the procedure, yielding low readings. Because the electrode will sense any oxidant capable of oxidizing iodidc, species sucl as manganese, iodate, bromine, cupric and cllor-oxy will initerfere. As with all ISE procedures, accurate compensation for sample temperature is necessary.
Atllougl it is claimed tat a MDL of 5 pg/L (as C) total o.icdant can be adieved (Ref 222,), this involves tighltly controlled conditions in tle non-linear area of the electrodc response. nhc procedure requires at least two minutes under constantstirring for a complete response.
Considering thle volatility of chlorine and iodile in natural waters, a practical level of detection using the electode method is doser to 50,ug/L Wilde (Ref22.3) compared the electrde method to the forward amperometric metiod and tlc DPD colornmetric method on standards anld cooling water samples for total residual cilorine at the Savannah River Site (SRS).
Statclard testing witi ligh purity water dosed witi cllorine showed no statistical difference among the tlree metiods. However, measurements made with the electrode on cooling w.iter samples were significanty lower tlu those obtained with the other two metlodms.
Wilde concluded the DPD method (using a Hach DR 100 Colorineter Kit) is tie recommended metold for future monitoring at SRS due to its simplicity and suitability for both field and laboratory measurements.
Table 2.2 lists the common metlods used for analysis of free or total chlorine disinfectints in water. Comparisons ar slhown for the analysis range, publisled detection or quantification limits, estimated precision and skiil level required to perform the tests.
Method Analysis Range Method (mg/L)
DLI (mgtL)
Estimated Precision
(% RSD')
Application Skill Levelt DPD Colorimetric 0-5 0.005 1-2%
Free and Total 1
ULR-DPD Colorimetric 0-0.500 0.002 5-6%
Total 2
DPD Tnration 0-3 0.018 2-7%
Free and Total 2
lodometrtc Amperometric Titration Forward Back up to 4%
up to 10 0.006-1.00 1
0.0012 0.0051 0.1 NR 1-2%
2-4%
Total Oxidants Free and Total Total 2
- 3 3
1 2
FACTS 0-10 10%
Free Electrode 0-1 0.05 10%
Total Oxidants
- Minimum or Estimated Detection Level
' % Relative Standard Devialion 1 = minimal training. 2 = moderately skilled with method. 3 = experienced NR = not reported Table 2.2: Comparison of Common Analytical Methods for Free andTotal Chlorine in Water 10
s9/19/2003 imes 11s49 AM T uxt+/-rPsat 914402905691 a.01-~
Pages 015-035
- 3. Method Interferences and Sources of Errors 3: Samppling Considertions A common source of error in testing for cllorine hi water is te fiilure to obtain a representative sample.
BeCcause fire chlorine i a stmng omdizing agent, its stability in naturl waters is very low. It rcadily reacts with various inrlUic compoundys and will slowly oxidize organic pomidi.Various factors, including reactant concentrations, pH, tcmperature, salinity and sunlight, ifIluence the clearsition of free chlorine hi water. Monochdoranine, on the other halnd, is much more persistalt i the envirounmnlt. Typically, the decay rate of monochlorarnine is tenfold slower than the recay of free chlorine in naturLl waters 7?q/T3 1).
Ideally, samples should be analyzed for chlorine on site. If sampling from a tap, allow water to flow at least five minutes before sampling to ensure a representative sample. Sample containers should be pretreated to remove any chlorine demand. Plastic sample containers slould be avoided because they might exert an appreciable chlorine demand aean glass sample containers should be pretreated by sxaking in a dilute bleach solution (1 mL commercial bleach solution to 1 liter of water) for at least one hour. After soaking, they should be rised thoroughly with deionized or distilled water or the sample. Another treament is required only occasionally if sample containers are rinsed with deionized or distilled water after use.
Do not use the same sample containers for free and total cllorine analysis. If trace iodide (from the total chlorine reagent) is carried over into the free chlorine detcrminltion, monodlorarninie will interfere i the free cllorine test. Ideally, separate and dedicated sample containers would be used for free and total chlorine determixhtions. A pre-trated BOD bottle, witl ground glass stopper malkes an idea! sample cotainer for chlorine analysis. For on-site determinations using Hach DPD calorimetric procedures, the one-inch square or cylindrical DR cell serves as an excellent sampler.
Avoid excess agitation and exposure to sunlight whlen sampling. Allow several volumes of the container to overflow and cap the sample contailer to eliminate head
.sae above the sTmple. If samp~llg with the DR cell, rinse the cell with several volumes of sample; then carefully fill to the 25-iL (or I0-mL) mark ForAccuVac Amnuls, collect sample il a vide-moutl container, suci as a bacer, rinsing several times with sample. Proceed with the analysis immediately.
If thle iodometric badc-titration metods (either visual or amperometric end poitt) are used for total chlorine determinations, the sample can be "fixed on site. MlTis involves th addition of a precise amounlt of standard reducing agent to the smple at the collection site. TMe fixing procedure calls for the adclition of 1.00 rnL 0.00564 N standrd thiosulfate or PAO, potassium iodide, and 1.0 mL pH 4 Acetate Buffer into a clean, dry glass container with a capcity of at least 250 mL (such as a BOD bottle). At the sampling site, 2(X) mL of sample are measured and carefully transferred to the.smple contaier and swirled to mix.
The delay between sample fixing and analysis should he minihmized (usually less than one hour) to prevent bacterial decomposition of excess thiosulfate (or PAO) in the sample. It is important tlt tie entire contents of the sample container be transferred to the analysis glassware used i the titration.
3b. Interferences Common to All Chlorine Methods All of the common analytical methods for chlorie or chloramines in water are based on clemical oxidation-reduction reactions. It should be emphasized that each of the chlorine methods is based on the total oxidizing capacity of te sample being analyzed aid is readily subject to inteferences from oter oxidizing agents.
Generally, all the accepted metllods for clorine are subject to potential interferences from particles, color, iorgalic and organic compounds, and buffer capacity in the sample. Unfortunately, tlre l nso nideal" mnethci for dlorine analysis wiidi is specific and selective for te free chlorine and chloramine species.
Other Disinfcctants I general, all of the common chlorine methods Vill detect other oxidants used as disinfectants -
such as chlorine dioxide (00), ozone (O,),bromine (Br),
hydrogen peroxide (HO,), and disinfectant by-products such as cllorite and cllorate -
if present i. large amounts. In the free chlorine determinations, these oxidlants, 1i sufficialt concentration, call react directly with the colorinetric indicator or will be reduced with thiosulfate or PAO in the titration mlLod. Each of these oxidants will oxidize iodide to iodine to a certain dcgree, thereby interfering n te total chlorine determination. Hach Comp-any has developed methods based on standard chlorine chemistries for Br, I and Analytical methods that attempt to distinguish between combinations of oxidLts try to convert all oxicints, except the analyte, to a non-ractive formL In reality, the extra equired manipulations may mnn somc loss of the 11
to 9/19/2003 Timai 11.4 A
To, Jutin_Pat 0 9,14402805681 Paqao 016-03S analyte, due to the extra time ivolved or changes of reaction conditions or the test.
MIanganese Compounds Mingainese Ui exist i oxidation states of +2 through
+7. The hlgher oxication states, typically +3 to +7, will interfere with all the common chllorine mcthods. Free cllorie reacts to oxldize soluble manganese compoune-. For example:
Mr + HOCI + 30t--MnO2 + Cl + 2H20 Ap;.rnirtly, cldorarines will not oxidize m:nganous compounds. Oxidized manganese will react directly with the DPD indicator. It is claimed that Mn (+4) does not interfere in tile FACTS method at a 1.0 rng/L level (Rf 3.2). At 2.6 mg M (+4), intederence is noted after five minutes with the FACTS test. Oxidized manganese (+4 to
+7) also will interfere in the ampcrometric titration for free chlorine.
Iodide can be oxidized by Mn (+4 to +7) to I, which will interfere in butdi the colorimetric and titrimetric metlods for total chlorine. Te interfeec of oxidized mnganese in bac-titration metlods appears to be a Iiiction of iodide concentration and the test pH (?ef.533).
The customary procedure to compensate for mangaese interference in the DPD methods is to first decllorinate the sample with iuitistEwili does not affect the mnganese, and then proceed with the test. The result obtained with the dechlorinated sample is subtracted from the normal test result to obtain the cormct chlorine concentration. Unfortunately, altenative reducig agents, suc as PAO, thiosullte, or ferrous salt, cannot be used because they also will reduce Mn, (+7).
Organic Chloramines There is considerable debatc over the Interference of organic chloramine compounds with the cited fre chlorine tesS. Organic nitrgen compounds can combine with chlorine analogous to the reaction with ammonia:
RNH2 + HOI -
RNHCI + H20 where R = the organic moiety Iypical oiranic nitrogen compounds would indude common amino acids and leterocyclic 1bases. Free chlorine reacts quiddy with these types of conmpounids to form non-germicidal organic clhoramines.
Published studies (R0 %3.4,35) have concluded that certain organic chloramines, especially N-chlorinated amino acids and N-chlorinated leteocyclic compounds, will iterfere vith all the common nnalytical methAods for free chlorine. However cllorinated anito acids do not appear to interfere in the free chlorine DPD and FACTS methods.
V~ite (Ref.I ) has contested the validity of organic chloraujine interference in the ampxrometric titration method. Based on his observations and surveys of wastewater disinfection systems, he contends that organic chloramines will be detected only as the didiloramine fraction when titrated in a forward ampemrmetrictitration.
At this time, the interference of organic chloramines in the free cllorine tests must be considered conditional, pending additional researcl Bromide in Chlorinated Waters Sea water and estuary water may contain natural levels of brolmide ions up to 65 mg/L The addition of chlorine to waters containing bromide will produce hypobromous acid and hypobtromite ion.
Br+ HOCI -. HOBr+ Cr This reaction is irreversible and the product will interfere with all common analytical proxcedures for free cdlorine.
If ammonia is present i the sample, HOBr will rcact with ammonia forming bromarnincs. Bromamines will reaa with iodide reagent analoously to te clloramuine reaction, indicating a positive interference In te total chlorine test.
It should be noted that bromide, when present in a chlorinated sample, forms a disinfectant (lypobromite ancl/or bronoanines) and, technically, te analytical results would indicate te total oxidizing capacity of the sample.
3c. Errors Cormnon to Total Cllorine Deteririnations All of the common total chlorine methods are bsed on the oxidation of iodide to triiodidc ion. Thiere are several potential sources of errors related to te iodide/triiodide reaction. They include:
- air oxidation of the iodide reagent
- volatilization of produced iodine
- iodine or iodate contamination i the iodide reagent
- consumption of triiodide by sample components.
12
i 9/19/2003 Time, 11t48 AM Too Juntin_Pat 9.1440280561 p&908 017-03S Potassium idid ragent is subject to air oxidation by the reactiorn 4r+0 2 +4H-212 +H 2 0 Tne reaction is accelerated by decreasing pH, light and traces of rrml ions. Ilodide reagent solutions are quite susceptible to oxidation fim exposure to light and oxygen. Research sponsored by the Electric Power Rescarch Institute (EPRI) has shown an amount of oxidant equivalent to 1 mg/L chlorine can he generated in one day in a 0.1 M (molar) Kl stock solution (Rzfs3 7).
An EPRI recorrmendation stipulates IC solutions be preparled fresh daily and stored in te dark Allaline iodide solutions apparently are mucl more stable to oxidation tl=l at neutral or low pH A trace amount of fxzse(e.g., sodium hydroxide) should be added to stock iodide reagent solutions for best stability.
Volatilization of free iodine fro-m the reaction of xidmnt with iodide is diminished somewhat in tlt excess iodide is present in the sample. In the presence of excess iodide, the less volatile triiodide ion forms. According to EPRI, the eror due to iodine volatilization will likely be only a srmll percent (Ref.3).
ie speed of the analysis also is a determinant for minimizing iodine loss by volatilization.
The purity of the potassium iodide is critical when measuring total chlorine at truce levels. The Iodide should be free of iodine or iodate, which can react directly with chlorine or dloramines or the indicator reagent itself. Even solid potassium iodide can be oxidized provided sufficient exposure to oxygen and ultraviolet occurs.
Adsorption of the produced iodine on suspended partidescan be a serious problem in mucdy or highly organic-rich waters. A perfect exaple of this type of adsorption is the blue complex formed between 12 and starch, the visual indicator for the iodornetric titration mehod. In addition to adsorption, iodine can react wAh organic matter to form crbon-iodine bonds (R.s39).
This is one reason for the traditional preierence of the back-titration metllods for total chllorine in sewage treatment plant effluents.
3d Interfrenccs in the DFD Methods Calibration Non-lnearity As stated in Section 2a, the reaction of chlorine with DPD results in two oxidation products: the colored WiUrster dye and the colorless imine. The proportion of colored to colorless product is related to the ratio of DPID indicator to oxidant. When DPD reacts with small amounts of cllorine, the Wirster dye product is favored.
At higher oxidant levels, the formation of the unstable, colorless imine is favored and results in apparent "fading" of the colored solution. It is necessary that the DPD:
oxidant ratio remain high to minimize fading of the resulting color.
TMe non-linearity of the DPD colorimetric method calibration using the Stndard Mehds; procedure h-as been reported by Gordon and co-worers (ef
- 10) and confired by Hacd Company chemists. The concentration range is stated to be 0 - 4.0 mg/L a,, using eitler chlorine stancrls or secondary standards made from potassium permanganate. Gordon rqorted the Standzml Metbod' procedure using permiagmate exhibited a nonlinear response above 1.0 mg/L equivalent chlorin. Hach Company also Ia s confirmed the non-linearity of the SzmidkMelXsd-c procedure using free chlorine standards.
ihe non-linearity of the SfrdaivMetJod; calibration (Figure 3.1) is attributed to the increased formation of the colorless imine product at higher oxidant concentration. In the Standard Metlhod' formulation, the amount of DPD added to the sample is insufficient to optimize the oxidation to the Wtirster product stage. he instability of the liquid DPID reagent is also a contributing factor to the non-linear chlorine calibration. As the DPID indicator solution ages, less active DPD free amie is available to react with sample cllorine, thereby shifting the DPD:oxidant ratio. This would lead to increasing non-linearity at the higher chlorie leveLs as the DPD reagent solution ages and becomes oxidized.
HadI COmplny has optimized its DPD reagent formulations to obtain a linear response to chlorine over the test range. Hach DPD reagents are controlled to assure lnearity over the specified range Because Hach DPD powdered formulations offer superior stability over the liquid reagent formulations, a reproducible and linear response to cllorine will be obtained for a longer period of time.
It should be noted that in the DPD titration method, both DPID oxidation products are titrated by the ferrous titrant As a result, the titration metolod does not suffer from the 'color fadig" plenomenon Precautions UsIng Pernanganate as an Equivalent Standard Dilute solutions of potassium permanganate are used in StaXndadMeJx~df as equivalent standards for establisling a cllorine calibration. It should be errphasized that pernuganate is a stronger oxidant ta cdlorune and certain precautionzs on its use and storage should be adnowledged. As noted by Gordon, et al. (Rc*
3-Q), permnganate oxidizes DPD to both the colored 13
a 9/19/2003 TIZZ10 11.48 AM Tot Juxtin_.Pea 0 9.144021O01
- a.
1.3 YaV 1 018-0o35 1.00 0.80 o
0.60
-o CD 0.40 tChlorine Standards 0.40 1 cm Cells Parabolic Curve Fit 0.20 0.00 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 mg/L Chlorine Figure 3.1: Standard Methods Calibration - DPD Colorimetric Method and colorless oXidation product. ach Company rcscardhers heave noted te order of adding reagent to sample also will affect the ratio of oxidized DPD products.
For r-xample, if the permanganate equivalent standard is placed in a container (such as a DR sample cell) and the free reagent is added to it, the oxicLunt is i excess during the akition process. Therefore, more of the colorless imine product can form, resulting in less color in the test.
Conversely, if the free cl-orine DPID indicator/buffer reagent is placed i the sample cell and permugnte is added to It, the DPD indicator remains in excess, with proper formation of the colored pmduct.
In practical terms, te differences between reagent-to-sample and sainple-tc>reagent additions using perrmnganate standards and Hach's DP) reagent are relatively small. Table 3.1 shows te differences obtained over a series of permanganate standards in the range of 0.2-1.8 mg/ as dclorine. The average difference between the vto addition techniques was 0.03 mg/ as dclorine. The greatest discrepancies were noted at concentratiorns greater tan 1.0 g/L It slhould be noted that te "order of addition" effect hyas been noted only when using permanganate standards.
Thls effect las not been noted when dilute chlorine standards were used.
A few precautions in the preparation and use of pernanganate standaeds are noted below:
- 1. Glassware used in the preparation and dilution of permanrpaate solutions should be treated with diromic acid cleaning solution to remove any organic contamination. Thenl glassware should thae be rinsed copiously %with pure water, whiclh is low in organics.
- 2. Water used for dilution of stock pernanganlate solution should be low in organics and should exceed Anerican Society forTesting and Standards (ASTM Type I quality specifications (R3 11). Dilution water for permanganate should never be stored in plastic containers or exposed to airborne contamination. Tic stock solution should be standarlized routinely witl dried sodium oxalate (f.5 12).
- 3. Dilute equivalent stancaLs are-not stable aid should be prepared as needed. Never store dilute penmangaiate in plastic containers.
14
9/19/2003 TiMQ% 11,48 AM4 ot J7Ua~+/-i.Peat 0 9,14402805681 Pag:
019-035 I
EquhaIent Reagent-to-Sample Sarnpl2-to-Reagent Difference I
gL C12 Abs Conc., rn g Abs.
Conc., mg'L Abs.
Conc., mg1L 0.20 0.108 0.20 0.109 0.21 0.001 0.01 0.50 0.271 0.51 0.271 0.51 0.000 0.00 n
9h A'7 n
%n
^
634 AQ frV nf A1I u.ou
- 1.00 1.20 1.40' 1.50 1.60 1.80 0.530 0.613 0.727 0.764 0.815 0.920 u.oV 0.99 1.15 1.36 1.43 1.53 1.73 U.4 0.543 0.632 0.743 0.791 0.834 0.928 V.0 1 1.02 1.19 1.39 1.49 1.57 1.74 u.uu XJ 0.013 0.019 0.016 0.027 0.019 0.008
%J. J I 0.03 0.04 0.03 0.06 0.04 0.01 Mean Difference 0.012 0.03 Standard Deviation 0.009 0.02 Range 0.027 0.06.
Using Hach Compans DPD Free Chlorine Powder Pillows. Cat No. 14070. and DR 3000 Spectrometer with pre-programmed calibrations Table 3.1 Order of Sample-to-Reagent Addition Using Permanganate Equivalent Standards Because of these constraints, Haci Company does not recommend the use of perrnanganate equivalent staidarrds with Hach DPD rmagents. Altcrnatively, Hadi Compan)y recomnmends the standard acditions technique using Clorine Voluette' Standarcds for routine verification of pre-programmed calibrations.
The Clilorine Voluette standards are pure aqueous free dclorine standards prepared in t ranges 30 mg/L or 50 - 75 mg/L chlorine. Tle actual value Is provided for each lot of stainkurls. H ind (orpany researcl hLas shown that tihe am-)uled clhloriae staldardLs exhibit excellent stability, when stored at temperatures between 2 to 8 C (33 to 470 F).
A simple procedure is used to verify the accuracy of the chlorine calibration. For example:
a) Snap the top off a ClhloritneVoluerleAmpule Stundard Solution.
b) Use tlheTenSerie' pipet to add 0.1, 0.2 and 0.3 mL of standard to tee 25-rnL samples. Swirl pently to mix c)Analyze each sample immediately per the Hach DPD colorimetric procedures.
d) EBca 0.1 rL of standard will cause an incremental increse in chlorine. The exact value depends on the Voluette concentration. Check the certificate enclosed with the VoluetteAmpules for this value.
Relr to Hacih Conranys WterAn4{s Handbook (RLc*f3 1.3) for more inforrntion on the staidard additio(s tecliique for verification of accuracy.
Monochlorurnine Interference in the Free Chlorine Test There is considerable controver-y about monoclloramine interference in the free chlorine DPD test. Some studies (Ref.3 14) lave indicated the percent interference in the free dclorine results can vary from 2.6 to 6.0/,,
dependlng onwthe monocloramine concentration and sample temp.erature.
The amount of monochloramilne must be substantial in comparison to the free chlorine concentration to inudicate an interference in the DPD colorimetric free chlorine determination. Tne reaction of DPD with free chlorine is rapid If the color is measured within one minute, the monochiloramine brealctirougli will tie minimal. A concentration of 3.0 mg/L monochlloramnine (0s Cl2) will cause an increase of less tian 0.1 mg/L free cllorine when ushig Hadi DPD colorimetric tests.
Monodlor-raine brealktirough is more of a problem in the DPD titrinmtric method for free chlorine because of the additional time necessary to perform the test.
StmdeaiMeb)dv recommends the use of thlioacetamide to "completely stop further reaction with combined dhlorinC in the free dilorie testTle thloacetamide modificition is recommended for the DPD titration of free dilorine in the presence of more tlan 0.5 mg/L clloranites.
Hadc Company does not recommend the use of thioacetamide in the free dclorine DPD titration or colorimetric methods for two reasons:
- 1. Tilcyaceramide las been shown to he a toxin and confirmed carcinogen.
- 2. The reaction of tiioacetarnide to prevent oxidation of DPD by ronochloramine is not thoro ughly 15
t 9/19/2003 Time. 11,49 AM To Juutin-Peat 9.144025S61P Page#s 020 -035 uncerstoocL It is not clear ift tioacetamide reduces DPD oxidized by monochlloramine or just reduces the combined chilorine. If it does reduce the oxidized DPD, why does it not reduce DPD oxidized by free chlorinc?
To catc, no independent validation or optimization has been conducted with the thioacetamide modification procedure.
If free chlorine is to bc tested in the prsence of i significant amount of monochlorarnine, the free cdlorine DPD colorinetric test is the reconcded rocedure.
Some published reports (Re/ft3.15, 3.10) indicate mercuric chloride, added to the tandantMethod.;
liquid plosphate buffer, has an inhibitory effect on monocllorarrifne brealthrough inl the DPD flee chlorine detemintation. The mercuric salt may scavenge trace iodide, thereby minirizing monoclioramine oxidation.
Herr againi, because this plienomnon is not completely uLnderstood and because of the toxicity of mercury salts, Hach Comp~any does not recommel or use mercury in any of its DPD ralt formulations.
Stability of the Colored Reaction Product 1nhe colored product formed on reaction of DPD with chlorine (or iodine i the total cliorine test) at neutral pH is a relatively stable, cationic free radical (?&
175).
Continued oxidation of the free radical will develop the unstable colorless imine compound and result in applarent hciig of the reacted sample color over time.
The potential forthe free radical to polymerize and form insoluble products also has been cited as a possUiility ibr reaction product istalbility (Refj 8). VA-Len limiting Ulie oxidation of DPD to the WLirster dye stage, it is important to optimize and control t ie ratio of indicator to oxidant.
A large excess of indicator should be avoided because this would contribute to the reagent blank and possible monocliloramnine brealthrmug.l Dissolved oxygen in the sample caii promote additional oxidation of the DPD colored product. Trace metals in tle sample and cpj-ure to light ray catalyze the oxidation (Ref.5.19). Controlling the test pH is importain because the reaction rate of DPD vrith oxygen is pH-dependent. Ideally, the reaction pH should be lowered if controlled oxidation is the primary concenI. Other factors, such as the presence of nitrites, must be considered Nitrites can occur under certain anaerobic conditions, and their interference will increase with decreasing pH. Had Compainy has found that a reaction pH controlled within the range of 6.0 to 6.8 appears optiirm for water and wastewater analysis with minimum interference from dissolved oxygen or nitrites present i the sample.
Sufficienit color developmcnt time is necessary to resolve didlorarunes at cold sample temperatures. Conversely, longer waiting times can result hi color fiiding due to further oxidation, polymerization or side reactions of the free radical. For successfil testing, espxcially hi treated effluents, strict adherence to the development time is necessary. Tree to six minutes of development time are sufficent to resolve all cllornamine forms without significant error from competing reactions.
Compensation for Sample Color and Turbidity One critical problem whena applying cclorimetric pro-cedures to treated wastevaters is iterference from turbidity and color ;n the water. For certain parameters, a preliminary filtration can be performed to remove particulate matter from the sample. lie residual sample color is "zeroed" at the measuring wavelength with tle cclor-measuring instrument.
StandazMethod; compensates for sample color and turb.idity sirply by zeroing the photometer with sample (Ref.320). This is appropriate for most colorinietric testing. 'mien testig for trace levels of total chlorine hi treated wastwatrer using Hachr Comany's LIR-DPID procedure, fie particulate matter may cause a "noise" level of up to
- 0.010 absorbance (using a 1"- pathlength cell). This level of variation is uacceptable when measuring trace color developed fmm the reaction of DPD with low concentrations of total dlorine.
Preliminary filtration of the water sample is not appropriate when testing for chlorine. Whether or not chlorine loss occurs during the sample filtration depends on the predominant chlorine species present i the s umple and tire nature of the filter media. Some loss can be attriiuted to the relative volatility and instability of cllorine compounds in natural waters. Adsorption of the hypochllorite ion on, or reaction With, certain filter material also can lead to chlorine loss during the filtering process.
Hadh Company studies indicate if the filtration is prformed eqfer the development of the colored product (a post filtration), removal of interfering sample turbidity caii be accomplisl-d without concern for chlorine loss.
Thc selection of the filtrr media is unrrortant because the Wurster dye product is a positively charged ion. Some membrane filter cornositiuins have a surfice charge that would exclude using them. The selection of filter porosity also Is critical i terms of adequate removal of the particle sizes that could interfere at the absorption wavelngthL In the ULR-DPDTotal Cllorine procedure for treated wastewater, sample turbidity is removed, using a syringe filter apparatus with a special inert 3-micron filter.
16
- 9/19/2003 Timwe 11t48 AM Too JustinPeat 9.14402805681 Pagel 021-035 A pr imary filtration Ls perfonred on the sample to zero uic photometer. A second portion of samiple is reacted witli the reagents and a filtration s performed on the reacted sample. Wen the post filtration procedure is used, the net asorbancc is adequately corrected for
.sample color and turbidity.
3e. Interferences in the Amperometric Methods StaradmeMethad.! states the arnpernmetric method"is the mktiort of choice because it is not subject to interfernce florn crlor, turbidity, ion, mnganesc or nitrite nitrogen" (Ref.21). In reality, several of these factors do affect the detcrnaiittion of chlorine species wAen using arnoxrerntric nthods. A brief review of some of the common sources of erors encountered with real world samples follows:
Deposition on Electrode Surfaces ClCan and regularly conditioned clectrodes are necessary for slarp amperometric titration end points. Because the electrodes contact the sanr:,le, certain species In the sample may plate out or coat tilC eectrode's metallic surface. Metallic ions such as copper (+2), silver (+1) and iron (+3) have been reported as either interkrences in the forward arnperometric method or may diminish the clectrode response. In some waters, foaming or oily surface-active agents will coat the ntnllic electrodes, resulting in decreased sensitivity.
For Had Company's dual platiurn electrdes (DPE),
regular cesaning and conditioning are necessary to remove any oxidation of the metal surfaces and to sensitize the electrodes to chlorine. Cleaning involves sklcing the electrode surfaces with a 1:1 NtricAcid Solution for a short period of time and then rising the probe repeatedly with distilled or deionized water The cleacd probe is stabilized by soaking the platinum electrodes in cilorinated tap water or a dilute (1-5 mgfL cilorine) solution of commercial blead, while stirring.
Allow at least 10 minutes for probe stabilization in the cllorinated water. Performing a couple of test titrations with chlorine or iodine standards prior to acmal samplc titration wiU furtler stabilize the probe. The frequency and quality of samples titrated will dictate the need for probe cleaning and conditioning.
Manganese Interference nere is a certain ambiguity hi the literature concerning rrnlganese interierence i the forward and back anperonmetric titrationis for cllorine. As explained in Section 3.b, if the sarrple contais free chlorine, any soluble mn-LuVg-nese will be oxidized.
Mji. HCI + 30t-Mr.O,
+ C 2H2 0 The oxidized forms of manganese (+4 to +7) will titrate with pleinylarsine oxide (PAO) in the forward titration procedure for free cllorine. Oxidized forms of manganese will react witl iodide at pH 4, producing iodine, whicl titrates witlh PAO, causing an interference.
Nitrite Interference Nitrite can eodst as a trnuisitory compound in certain
-.waters, due to the biological oxidation of ammollia:
2NH, + 30,- 2NO,- + 4H' + 2O There is conilicting inforration about te interIerece of nitrites in eitler the fordwa or backward amnperontric methods for total chlorine. Accoriding to Stan drt Method', nitrites do not interfere in the forward titration methods (?ef 322). Stan d Metbod section 45i0O Ch., the lodometric Mctlod II, states that nitrite interference can be minimized by buffering to pH 4.0 before addition of iodide. It also states tlat interference from more tla 0.2 mg/L of nitrites can be controlled by the use of a phosphoric acid-sulfarnic acid reagent. Tlis reagent is used in conjunction with iodate as titrant because higher acidity is required to lerate free iodine.
W\\lite (Rcfg323) indicates nitrites can oxidize K to iodine, similar to the reaction of KI with chlorine or dlloranines. The reaction of ECI with nitrite apparently is accelerated by acidity, esecially when the pH is less tlan 4. Wlite recommends the addition of suLftamic acid to tle sample containing nitrites and allowing it to stand.
for 10 minutes prior to the adlition of standard reducing agent. Thiis procedure cks not, however, address the possible loss of clloramines or side reactions during the delay period.
Hach Corr4any rsearclfers, using te forward-and back-titration procedures, have investigated the effec of nitrites i the determination of monoclloi-amine.
Monohldoramine was selected since it is slow to react witli nitrites (Ref.324 ) and represents the primary disinfectant form in treated wstewater. Free cllorie has
,een slown to react dir'ctly with nitrites (Ref 25) acconling to:
HOCI +NO-NO3-+ HCI To investigate the effect of nitrites on the determination of low concentrutions of monochlorarrinte, six variatiozis in the amperometric procedures were.studied
- 1. Forward titration witl K1 added first, then pH 4 buffer (PAO as titrant)
- 2. Forward titration vith buffer added first, tlen K (PAO as titrant) 17
j 9/19/2003 Times 11e49 AM Too Justin-Peat 9,144020056E1 Pages 022-035
- 3. Back titration, excess PAO, la, then pH 4 buffer (iodine as titrant)
- 5. Bac titration, excess PAO, K, then H PQ4/sulfamic acid (iodte as titrant)
- 6. Bac titration, excess PAO, H,PO,/suLianic aid, then M (iodare s titrant).
No. 1, No. 3 and M. 5 follow the SandazfMethlxdi procedures for fornvard titration,back titration witl ioline, and back titration with iodatc, respectively. The testing for No. i trugh N. 4 W5as performcd at pH 4, because this is the pH used to speciate 'totl"cilorine.
All of the titration end points, werc determined amperometrically.
A ionochllorarnine stan chrd was prepared in the range of 70 to 80 ;g/L (Cl,). Snrll portions of a stock nitrite
.tminclrd, equivalent to the addition of O to 50 irg/L nitrites, were added to 200 mL of the monocnlorarnine standart. Analyses were perfonecl in triplicate accordi;ng to the sequences listed above. Mean percentage recoveries as a finction of nitritc concentration are showI gruphically in Figure 3.2.
In variations No. 5 and No. 6, witl the addition of nitrite to the cllorinc stanaard, a large amnnt of iodine WJs generated almost instantaneously after the addition of tle reagents. This suggested tlat nitrites, at concentrations between5 55-() m&/L, will react readily witl iodicle at the lower pH, even in the presence of excess reductant and sulfanic acid. Standand Met )od, directs the analyst to "titrate immcdiately" withi iodate. Hacn Comjxuny studlies, liowever, ilicate nitrite as low as 5 ngL will 'break through" within 30 seconds after addition of the K! and acid mixture.
[n the forvard titrations (No. 1 and No. 2), nitrites seem to inxicute either a positive or negative interfernce depenmding on the order of reagent addition. If iodide is added to tie sample prior to pH 4 buffer, the error increases as a function of nitiite concentration. If buffer is added prior to the iodide, a large negative error, independent of the nitrite level, occurs.
The preferred procedure, indicating the least interference frm nitrites, is the bacc titration at pH 4, using standard iodine titranit, (No. 3 and No. 4). Thie iodometric procedure in whiid 1 is added first, tlen buffer; seems to provide the least amount of variation witl increasing arnounts of nitrites. Tlis procedure is recorrended for 200 180
- 1: Forward (KI, Buffer CD 160 140 t_
Y~~~~~~~~~~~~~~~4:
Back, odine (Buffer, I) 120 __
o
-~~~~~--
>,00
- -.E~-
'#3:
Back, Iodine (KI, uffer) 0 80 i'
60
-G___
40
- 2: Forward (Buffer, KI) 20 0
1 0 20 30 40 50 mg/L Nitrites Added Figure 3.2: Nitrite Interference In Aperometric Chlorine Methods 18
- 9/19/2003 Times 11s48 AHM Tot Juxtin_.Pea 6 914402905681 Pages 023-035 the anerometric titration of tot chlorine in treated Nvastewaters, agricultural waters and industrial disclarges.
H-lich oanzly las dcvelolped a convenielit amperormetric back-titration procedure using Standard Iodine trant, 0.0282 N Lch Grr4?any researlers have investigated the factors which affct stability of dilutc aqueous triiodide (1,)
solutions. A stanlard iodine titrant, wiich is Stable for nontlis when stored at moderate tnmpxraturcs, is now availablc. With micro-dispensation of the titrant and automatic determination of the titration end point, total chlorine levels as low as 1.2 pg/L can be detected.
Choice of Reductant In the forward amperometric titration metlod, it is isrortant tlat only phenylarsine oxide (PAO) be used as the titrant wlhen measuring total chlorine. PAO will give sarsper end points tlan standard thiosulfte at pH 4.0.
This is shown comparatively in Figure 3.3. Thc titration plots show the titration of an 82 pg/L monochlorarnine standardl, using a continuous titrant feed of. a) standard thiosulfate and b) standard PAO. The rate of reaction of Senerated trilodide with titiosulfate evid-tly changes as the end point is approacled. This can lead to a certain amount of uncertainty when determining the end point graphically (as indicated in Figure 3.3a). The use of PAO gives a relative sharper end-point determination (Figure 3.3b).
In the case of the awperorretric badc-titation method, the addition of either excess PAO or thiosulftate is acceptahle. The titration end poillts for both reductants are equivalelt when stancard iodine is the titrant.
Effect of Iodine Demand on End Point Determinaiions Gertain saxrqls containing orlnic compotinds may exhit an' iodine demand"'that cln shift the titration end point, even when a bac titration procedure is used.
EP(1) = 45 EP = 82 EP(2) = 82 Figure 3.3a:Thiosulfate asTitrant Figure 3.3b: PAO asTitrant 19
, 9/19/2003 lMes lle48 AM To, Juatin-Peat 914402805681 Pages 024-035 An example of this effect is shown in Figure S.4. If the sample contains suspended partides, generated iodine will adsorb readily onto the particles, resulting in a shift of the current rcadings. In addition to adsorption, iodine can react with dissolved orginic matter in the sample forming carbon-iodine bonds.
lForsamples containing appreciable iodine demand, some difficulty will be encountered in aclieving an accurate estimration of the end point. Continuing the titration to obtain several readings after the end point will hep in the ilterpolation of the ts intersectig lines. Also, the spee-d at whicl the titration is performed vili be a factor in minimizing iodine demand and identiing the actual end point. Dilution of the sample with chlorine dend-free water also will minimize iodile demand, although witi a certain sacrifice in sensitivity.
Order of Reagent Addition TMie re-asurement of cl-dorine in saline ad estuary.water or sea water is exceedingly difikult with any of the available anlyticil methods. There is a certain amount of conflicting information in the literature pertaining to the amperometric determination a total chlorine in salt water. Several studics have indicated the order of K[ and buffr reagent addition may cause underestimation of the total chlorine concentration when determined amperonotrically.
It should be emphasized that the chemistry of chlorine in sea water is exceedingly complex. Salie waters usually contain an appreciable chlorine demand, due in part to oxddation of carbon aid nitrogen-containing corzounds.
Bromide, usually present i sea water will oxidize to hypobromite when chlorine is added. Furthiermre, the concentration of chlorine-containing and secondary oxiclants produced by chlorilation are dependent on the characteristics of the water being chlorinated such as salinity organic load water temperature and incident sulight.
There is general consensus that iodide reagent should be added betore or aimultaneously with the pH 4 bufter in the arrqpromet ic determination for"total chlorine" in saline waters. If the saline sample is buff-red prior to addition of the iodidce, the tomal oxicant concentration may be underesimated 60 48 CO 36 acis a" 24 12 0
Volume of Standard Titrant Figure 3.4: Iodine Demand - BackTitration 20
- 9/19/2003
- Tima, 11.48 AM Tot Justin_Peat 9,14402B05681 Paq9m 025-035 4k Method Comparisons and Performance Evaluafions Several comparative studies of the anlytical methods for dlorine analyses hivc been published For a compreresive survey of laboratory method comprisossee AWWA's DLdnfeant Res*Idual AMea inemezt Methxtls (Ref 4.. A surnimry of publised studies which lave compared ie Hach DPD method of analyses to otlier chlorine methods appears below. A note of caution is advised in tie interpretation of early method comparison studies because the tecmhology has improved over the years.
4a. Field Mit and Laboratory Conwarisons
,978: UNEPA-EMSL Report EPA 600/4-78019 "Comprison of Mctlod for the Detcrmination of Total Available Residual Oilorine in Vaious Sanple Matrices" by Daiel E Bender This study compared 10 methods for the measurement of total chlorine hn various matrices. Three versions of the DPD colorimetric method wre used: tie Stzmdan AMetb Ixls 409F, Hac Company's CN-66 visual corrarator and the Bausd & Lori's Mini Spec 20 Kit. The samples studied were: spiked distilled water, river water, sewage plant influent and effluent, and unspiked tap water ie iodometric forward titration (IFI) was chosen arbitrarily as tie reference metiod. MIe accuracy of each method was expressed as percent recovery of total chlorine compared to the [Fr method Precision was estahlished from tie relative standard deviation
(@IRSD) derived from replicate analyses at a certain Conlctiratiol.
During this study, Hac Company's CN-66 produced unacceptably high recovery (134 4) in drinling water and low recovery (525),? in river water matrix but only slightly high results (151090A in distilled water and scwge effluent rmtrices, compared to tie IFT method.
Turbility and ceep straw color of tie sewage influent sample prevented it fim being tested by tie comparator.
Precision for te CN-60 wvas "rearlribale' a5% RSD),
considering a comparator wLs used.
titrator and an Orion ion selective electrode (ISE) on standard -nlutions and cooling water salIes at the Savannah River Site nuclear facility.
Testing of chlorine standards prepared in high purity waterslowed no statistically significant difterence among te three analysis metlods. In contrast, the results on unclilorinated, chlorinated and chlorinated/decllorinated cooling water samples indicated mnat te measurements with te Hachl DR 100 did not differ significvtntly from measurements obtained with te ;r'pqromettic titration metliod. Measurements made with thu ISE method, however, were significantly lower tan tose made with tie DPD and amperometric mctliods.
The author concluded the DPID metlod using Hach Corrpany's DR 1(X) is the most appropriate tedmique for future monitoring of residual chlorine at te Savannah River Site. Simplicity and suitability for both field and laboratory measurements were determining factors.
1993: Witer Evimnment ResearebVolume 65,No. 3,
- p. 205-212 OComparison of Free and Total 3llorine Measurement Methods i Municipal Wastewater" byJames Derrigan, Li-Yin Lin, andJames Jensen In this study, four titrimetric methods for total cllorine (iodometric witi starch end point, forward amperometric, baec amperometric and DPD titrimetric) were compared in1 testing chlorinated municipal wastewater samples. In addition, on-site measurements were made using m unspecified Had Company test Idt based on te DPD colorimetric method.
Cmrs coinmparisons of te data from all tie metlods on six samples collected from te dlorie contact basin indicated te plant readings witl te on-site DPD calorimetric cit compared favorably with tle laboratory results. Although the study was limited in the comparison of Hacl Company's DPD metlod with the StandatIJMethxod titrimetric procedures for chlorine tde authors concluded tde on-site DPD colorimetric redings were in agreement with results obtained with tde forward and bactc amperometric titration mediods.
1991: Water oeura;Volume 25, No. 10 p. 1303-1305
'Compfarison otnulree Metliocls for Measuring Residual Chlorine by Edward W Wilde Rcsults obtaied when using a Hacl Company DR 100 Colorirneter for total residual chlorine were compared to results obtained from a Fisher cllorine amperometric 21
- . 9/19/2003 Time 11.49 AM Too JustPeat 9.14402S05661 PaVQI 026-03S 1993: Proccedings of the 6th Water Environment Federation Confereice OApplicaion of the DPD)
Colorirric Metiod for MeasuringTrace Residual Chlorinc" PaperAC93-059002, by Danial L Harp Had Comny's ultra-low range chlorine DPI (UIR-DPD) method was compared to the StanLdard Metiods hack armnprnmetric titration metiod (45(X-Cl-)
using ioxie titrant on nine geographically dispersed samples.
Treated wastewater samples were obtained from large and small publicly owned treatment works, an electric utility, a national security installation, an inorganic chemical manufacturer and an organic cliemical manufiacturer. Thc samples represented diverse matrices of domestic sewage effluents, cooling water. boiler liowdown and manufacturing wastes.
Samples were treated with a suitable amount of lypocilorite to satisLf any cilorinie demand Wile samples were aging hi te dark luder nitrogen gas, cllorinic was added to obtain a total chlorine residual between 5 - 400 /L Aliquots were drawn t vrying concentration levels and tested by botl tlie ULR-DPD and back anipernmetric methlods. At least eiglt data paiN (ULR-DPD vs. Amperoetric) were obtained for each sample witlin tle 5 - 4(X) pg/L dldorine range.
In addition, a small amount of knovwn 1yj)ChloriTe addition (a "spike") was added to a second aliquot of eachi sample and tested by the two analysis rethods.
This providel an estimate of the accuracy of the methdLs, as percent recovery of the spike.
Figure 4.1 sl-cws the results of the metlod comparison study of all aired data. 1IC 45 °- line represents 'ideal" correlation betwen tie two analytical m.cthocds. Statistical evaluation of the data, using analysis of varince and a pairec} t test at a 95% confidence level, indicated measurements made with te UIR-DPD metlod did not differ significantly fmnm measurements made witl tie back amperometric method witinii this concenration range.
25-0 01 E
0J50
- 0) 0 100 80p
>0.05 GD~~
50-0 I
IIIIII 0
50O 100 150 200 250 300 350 400 ug/L, ULR-DPD Figure 4.1: Method Comparison Data: Ultra-tow Rqange Chlorine Methods 22
v 9/19/2003 Times 11.49 AM To, JumtinPeat a 9.1440280561 Pages 027-03S Tnh percent recoveries obtained from the spiked sample data ranged fiom 82.8 to 97.81%/ (mean = 90.5%) for the TJLR-DPD method aid 92.5 to 136.6% (rnea= 112.0) for the back aiperometric method 4b. Performance Evaluations of Process Analyzers for Residual Chlorine
'Te Water and Wastewater Instrumentatibn Testing Assocation (ITA, formerly knowvn as InstumtTesting Se-vice) ha conducted tvo comprehmisive evaluations of residual cllorine analyzers (Reft 42, 43). ITA is a non-profit assocation set up to perform independent testing and evaluation of instrumentation used in the water and
%vastewater treatment industries.
The initial MA effort was the assessment of total residual clorine CQR analyzers, performed during 1983-1984.
The testing program induded bencli analysis of on-line TRC analyzers under controlled conditions and field testing at a wastevater treatment site in Ontario, Chnida.
Bend testing was performed on four different analyzers:
two based on ampcrometric detection. one based on pozentiometry, and Hach Company's Pump Colorimeterlt~ Analyzer (PCA), based on the DPD colorimetric analysis. 'The belclh testing program involved a series of tests to evaluate the mechanical and.
electrical cormonentts of the instruments and instrument performice under standard conditions.
'Three analyzers representing amperometric, potentiornctric and colorimetric detection were used for field testing. Protocol for thr field evaluation Included long-ter-m performance, calibration, resporse time, interferences and general design faactors. The DPD colorimetric method vas selected as the reference laboratory test method forTRC in the analyzer evaluatiolns.
The bench-test results demonstrated the adequacy of the electrical and mechanical components of the instruments.
hI gaineral, the instruments performed per specification during the bench. wet tests. Haci Conpany's PCA slord relative isensitivity to either saqle Temxraturc or ambient temprature fluctuations. The minimum detectable limit was determined to be 0.009 mgfL as C.
for the PCA Reld testing results indicated the PCA's accuracy, response time and recovery time were relatively unaffected by continuous exposure to wastewater after 60 days of exposur. The PCA was the only analyzer not requiring nmintenance beyond routine calibration and reagelt replacement during the evaluation period.
The 1TA research group concluded the Hach Compny Pump CAlorimeterAnalyzer overall exhibited accepted accuracy over Its normal operating range, and accuracy and response were unaffected by exposure to wastewater or by temperature dmgesr A second, more detailed evaluation of residual chlorine analyzers was conducted by the E during 1989. In tiis study, both free and total residual cllorie analyzers were tested Six different manufacturers' on-line chlorine analyzers were tested on the hench and in the field The analyzer types included three based on amperometry, one with a polarographic probe, one witlh an iodine ion-selective electrode, andx Hacl's CL 7 free and total cllodre analyzers, based on DPD colorimetry.
The bench tests assessed reproducibility, response, noise, calibration, detection limit and tempxratur effects under controlled conditions. Field tests consisted of operating the free chlorine analyzers at an operating drinlchng water tratmen plant and the total dlorine analyzers at a wastewater treatment plant for a pcriod of 45 days.
Accuracy of the analyzers was judged in the field twice daily by comparisons to laboratory results. In addition to quantitative tests, each instrument was subjected to a qualitative analysis to assess operational and mainte=nce performance in the field The CL17 analyzers exhibited good accuracy and reproducibility with. little temperature ef£ects. In addition, the instrument indicated one of the lowest detectable concentration levels of all analyzers tested at 0.013 mDfL Cl.. The total chlorine CL17 showed the least interferrnce vw1e compared to the other commercial chlorine analyzers.
Relatively high mintenance (40 events) was required for the total clhlorin CL17 during the field testing. This was due to sample line blockage, sample strainer cleaning, sample line tulbin replacement and sample cell cleaning.
Since the flTA evaluation, Hach Company has developed a self-cleaningYsrainer designed for use with the CL17 analyzer. The strainer has since been shown to reduce maintenance requirements significantly in wastewater applications.
Complee test results for the bench and field evaluations of Hadi Company's CL17 analyzers along with evaluatiors of competitor cllorine analyzers can be found in ill's report, eifjirnance Evaduatin (if Re'dal OilzotneAnacyzerJbr Water and Wciteurzter TreahmentApplcatUn, Report C-1 (Ref 43).
i 9/19/2003 Timat 11.49 AM Tot Justin-Poat 91440200561P0 PAVOIl 028-035
- 5. Selection of the Appropaiate Yesting System The selection. of an analytical system for chlorine testing will depend on several Jictors and situationis. For exarrple, if dlorine testing is performed to meet regulatory compliance, the selected method must be acceptable to the regulatory agency. Under certain sitiations, the use of visual field test kits will provide acceptable results. Some situations require inear continuous analyses using a process analyzer The following will provide guidance in selection of the most appropriate chlorine test system for a particular situation.
5a. FIeld Testing Test Idts using color corrxmrators or colorimeters hased on the DPD colorimetic ntiod are ideal for measuring free or total chlorine in water on site. Table 5.1 compares the Hachi Company DPD platforms des-igned for field testing.
Many of the visual comprator DPD ldts are used for public and private swimming pools, aquariums, small and large industrial processes and small potable water treatment systems. These types cf systems typically screen or check for maintenance of a cllorine residual.
Higi degrees of accuracy and precision are not required and a visual color match is sufficient for estimation of the cilorine level. Color matcling can be in the form of incremeital steps, as in the Color Cube, or in the form of a continuous gradient, as in the Color Disc.
Test kits for measuring residual cilorine following the DPD methodology are recommnided by the Vbrld Health Or~thiation (WHO) in pidelines to smnall cormunity supply systems (RLf5.1).
In recent years, the coicept of on-site testing witli a small, portable colorimeter las matured Colorimejers eliminate the luman errors associated witi color matching.Hach Company pioneered this concept with the intmductioi of the DRand DREL portable colorimeters for chlorine testing in the 1960s. Tie first handlild colorimeter for chlorine testing, the DR 100, was introduced by Hach Company in 1980. With the advent of accurate digital electronics, portable colorimeters have become more compact, durable and versatile. Examples of the latest teclnology trend indude tile Pocket ColorimeterAI, the DR/8M Portable Colorimctcr' and the DR/25() Spectrphotometer.
Most of the testing platforms listed in Table 5.1 are acceptable for testing free chlorine or chloranines hi potable water. Most pot2ble watcr suppiies iir low in color and turbidity and show little lenical interference in the DPID metiod
,Many water utilities have scattered chlorination stations throughotit their distribution systems. The best choices for this case would be a CN-70, a CN-80 or anAccuUac color disc test kit, or a portable photometer system stich as the Chlorine Pocket Colorimeter. If additional parameters are tested at the chlorinating sites, a CEL/SO or DR/2400 Portable Spectrophotometer should be considered.
Many states regulations allow the use of DPD visual comparator kits in fulfillment of residual chlorine reporting requirements under the Safe Drinking Water Act. Local or state regulatory agencies should be contactod for bpecific information on the procedures and equipment specified for chlorine testing in each aret.
DPD test Idts and photometer systems are used rutinely for monitoring free and comined chlorine resid' rals i treated wastewvaters. If the wastewater is highly colored Type of Measurement Platform Product Exampies Test Ranges' (mgIL)
Visual Comparison Colorimeter Spectrophotometer Trtration Color Cube Color Disc Pocket Colorimeter DR/800 DRt2400 Digital Ttrator DPD Color Cube CN-66 lest kit CN-70 test kit AccuVac' Reagent Arnpul Pocket Colorimeter Cl2 Kit CEJ800 Lab DRt2400 Portable Spectrophotometer
- DPD-FEAS 0-2.5 0-3.5 0-0.7, 0-3.5 0-2.5 0-2.0,0-4.5(T) 0-2.0(F), G-3.5(T) 0-2.0, 0-5, 0-10 0-3.0
' applies to bot 'ree and totaruntess otherwise noted (F)
Free Chlorne (T) - Total Chlorine Table 5.1 Hach Company FeldTesting Systems for Chlorine 24
t /19/2003 Timet I1t49 ).H Tot Justn_.Pea 0 9.4402805681 Page 029-035 it may be more practical to use te DPDTFAS or ioclometric titration metodLs with the Digital Iltrator for fied testing. If final declilorinated efiluent is tested, the UIR-DPD procedure for total chlorine can be used In conjunction with the porable DR/24(X)
Spectroh:otometer for on-site testing. Haich Company's DPD cleamistry Is accepted by the USEPA for total chlorine testing under the WDES progran. Local or state regultory agencies slould he contacted for specific ar=
information about total cliforine testing equirements for permitted disclarge waters in that area.
Echl o the visual comparators and the field instruments use te sare proven Iacl Company DPD coloLimeiric chlemistry for chlorine testing. The amount of reagent fill per paage (pillow ampule, or container) is adjusted for the sarrnple volume uscd - usually based on 5-, 10 or 25-miL san4le sizes. Mie concentration range Cal be extended by varying the sample cell pathlelngt and adjusting the reagent to sample ratio. For example, in the CN70 and CN-80 color disc Idts the sensitivity can be increased by using lengthwise viei.vng.
5b. Laboratory Testing JIdeally samples for chllorine analysis should be tested on site, as cLesaibed in Section 3a. But if sample holding times allow, the best accuracy and precision for cllorine analysis are obtained witl laboratory analyses. Iaboratory methods for fee and total chlorine include the DPD method -
using a spxctroplotometer the amperometric titration metlods and the titration medods witl a visual colorimetric end point.
The DPDI metlod using Hadn Companuy's DPD pillows and a DR/2500 or DR/4000 Spectroplotometer is recommended for mutine laboratory testing of free and total chlorine residuals. The linear ruge for the spectroplotometers is 0-10.0 mgL a,. H.tlier leves of chlorine can be determined by dilution of the sample with chlorine-demadfree water. Wien samples are diluted, some loss of cllorine may occur. Figure 5.1 illustrates a decision-tree for selecting the proper chlorine test.
The spectroplotometerprocedurs use *i standard 10 or 25-ml. sa=ple size. Alternatively, reagents pacaged into AccuVac"Arrpuls can be used for carrying out the chemistry and measuing the color with a spxctrophotometer and special cell adapter.
TMe patented (Ref.2) Utra-Low Range DPD (ULIR-DPD) colorimetric method for total cllorine uses a flow cell with eitlher a DR/2500 or DR/4000 Spectrophotometer.
The "uur-Tlru" cel eliminates optical errors caused by using discrete sample cells and contributes to accurate measurements of low color absorption. A filter asscrnbiy is required for highly turbid samples. FR-maudnium sensitivity, the color measurements are made eitler at 510 or 515 lnx.
Mhe range for tle LIR-DPD method is 0-500 pg/L dlorine witl a metld detection linit (MDL) of 2 pg/L The UIR-DPD method is accepted by tle USEPA for rqorting purposes under the Safe Drinking Water act and the NPDES permit program.
Hadi Company offers several pncedures using HadiVs AuoCatm 900. Pircdures are available for total dliorine forward ttuaticx, range 0.0012 - 5.000 mg/L Q, total dlorine lick titration, range 0.(X)52 - 5.(XX) rngL
, and free dlorine, range 0.100)5.000 rmJ/L a.Ranges c *n, be extencled by sample dilution.AlM of Hach. Cnm1 ralmys an4eromernic titration procedures are based on Sta danI Metbxx& 450-orLbEPA Metiod 330.
Which Chloride tnst M."n V a ppliCatio rq.'I?
I I
I I
. I I
I...........
sets. iWiFAACCepted a' Appre; Rcftto te I
ZnpnetctnI I
C1hart
.'- l.,__
F r.lmfion II I SI 1AL FE LCO~ n-tho. by I&ange-
___71 I
'jI ;L>
TOTAL
-Ii
- 1-5
]
it
-I FREE ~
~
EUE Mclho1 8203 OIGITAL TITRATOR 0-2."gL 0-2 "IL M~th*Wf0060 I I 0-21L0 Meho1867
~
Mnthod1 60211 Rarpd bU..,
- 0.
CI-I mgL 1T_1 Meho Ath~rf0101 OPO Mh/d r
lor an wttr TNT
-r appl.cat-oM-O r usle Method1 10014 06mI tot wasta-atet
,gthorl 0021 appictofls.
TNT
'Under USEPA N.t~o.
PIl.t.,,t 0,SCharge E__t.i, Sstc-~
o Sn Ck..it.ng Water ct tegi.Iat~onl.
I I
I.
II i"
Figure 5.1: Selection of the Correct AmperometricTitration Procedure 25
s
/19/2003 Tims 11i49 M Too JuxtinPost~ a 91440290S691Pae0003 PatJes 030-035 Figure 5.2: CL17 Chlorine Analyzer PIi Company titration rDtlo(s for chlorine also include te iodometric metiod using sodium thiosulfatc as titraint and te DPD titration metlod using frrous ethylenediammonium sulfate (FEAS) as titrant. In these procedures, the titration end point is indicated by a visual color clange.
5c. On-line Antomated Testing The Surface WterTreatment Rule issued by the USEPA (Ref 53) requires thiat residual clorine be molitored continuously on distributed.ater for systems serving more tlhm 3300 persons. The CL17 GilorineAualyzer (Figure 5.2) is used extensively at te point of distribution to ensure adequate cllorine residrals. Tle CL17Analyzer also is used i cooling water treatment to prevent bio-fouling, in reverse osmosis systems to protect membranes, and i wvastewater treatment to ensure regulatory compliance.
Thne amilyzer is equipped with a two-reagent system based on the DPD chemistry. The DPD Idicator Is prepared by adding the powdered DPD reagent salt to the acidic idicator solution. The powder readily dissolves in the solution and the mixed solution is stable for at least two months. Great care is exercised in namnufacturing tie DPD reagents to ensure the DPD Indicator Solution does not contain Ipurities whiich can promote oxidation of ionic DPD. After dissolution, the DPD Ildicator Reagent Solution is free of insolubles which can exibit a reagent blank or plug reagent tulbing.
The buflcr solution for the total cllorine QL17Anlyzer is a citrate-t)pe wlidi also contains iodide. The Free Qilorine Buffer Reagent is a maleate-type buffer.
Thc buffer rcagent and its complementary indicator rcagent are added in equal volumes to a captured portion of sanplc. Pre-mixing the tvo reagents before introduction to tl sample is important. This is accomplisled by incorporating a 'T union in the reagent feed lnes prior to the colorimeter block.
The operation cycle of the CL17Anialyzer is summarized as follows:
- 1. Sample inlet line of the pump/valve module is opened, allowing pressurized sample to flusli sample tubing and the colorimeter sample cell.
- 2. Sample Inlet is dosed, leaving fresi sale in the cell. Cell volume is contmlled by an overflow weir
- 3. As samp!c inlet line doses, reagent les open, allowing buffer and indicator solutions to fill tubig i the pump/valve module.
- 4. Reference measurement of untreated sample (a sample blanc) is made prior to reagent addition This compe:nsates for sample color and turbidity.
- 5. Reagent outlet blodc opens, allowig precise volumes of buffer and indicator to blend and enter the colorimeter cell to mix witl sample.
6After about a one-minute delay for fill development of color, measurement of the magenta color is taken at 510 nm (the sample measurement).
- 7. Concentration (as mg/L cllorine) is calculated by the log of the ratio of reference measurent to sample measurement, and then displayed Tile cycle sequence is repeated every 2.5 minutes.
For the on-line determination of total chlorine, the color development time required las been slortened by varyig tle test acidity and increasing the iodide concentration i the sample. Consider the reaction chemistry of diclloranine:
NHCI2 + 3- + H2 0 + 2H'
- NH 4OH + 2Cr + I 13- + DPD 31- + DPD (oxid.)
Thc rate a the first reaction is mucl slower tlan te rate of the second The speed of the dicliforamineiodcide reaction can be increased by increasing the ioclide addition and/or adjusting the acidity. Acidity cannot be significantly increased, however, because of increased nitrite interference at a lower reaction pH 26
s9/1.9/2003 Tumes 11t4 A Tot Jaustn.iPeat
- 9.14402B05681Pge03-3 Pages 031-035 Hadh Corn4pany c.!emists have optimized the ainlyzer reagent formulations t c quantiatively measunt 5 mg/L dcilhoranine (as 0) at cold sample temper tures
,witlout nitrite interference and within the one-minutC color-development time.
- 6. Conoluslons Currently nogidealamethod exists for quintifying clilorine and dloramines i water All common metliods of cllorine analyses display some lack of specificity and arc not adequately selective to be completely free of interfermces.
Fourteen conceptlm qualities of an ideal" metod for clilotine anlyscs were presented inAWWX.As Disinfectant Residual Aeasurement Mthlods (Rf 6. 1). The 14 qualities are:
. BEing method specific to the actal species (e.g., free cllorine = HOG + Oa-).
- 2. Possessing a selectivity of at least 500 times over possible itereralces.
- 3. A retection limit of ppb as Q,.
- 4. Precision of :t 0.1% or Iextter
- 5. AccuracY of *t) 0.5% or better
- 6. A linear wodng runge of four orders of rrzagnitude.
- 7. Perornance witl any sample matrix.
S. No requirement for sample dilution io minimize interferences.
- 9. Vrdlng in both batch and autornated modes.
10.Nimum sesitivity witlitraditional laboratory instruments.
- 11. No specialized sldlls required tco perform the test.
- 12. Reagent stability in excess of one year
- 13. Performance of the test witliin one minute.
- 14. Being cost-effective.
An arbitrary rating of the common cllorine analytical metlods -
based on the authors expertise witl each method -
was conducted The information aplxas i Table 6.L Five of the aralktical methods are Hach AWWA Ouality Concept DPD DPD lodometric Amper.
Color.
Titration Titration Forward Amper.
Back FACTS Electrode 1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
Specificity Selectivity 1 ppb MDL 0.2 % Precision 1 % Accuracy 4 Orders Unear Range Any Sample Matrix No Dilution Required Can Automate Traditional Instruments No Special Skills Siable Reagents Fast Procedure Cost Effective 5
7 2
4 6
5 5
5 7
7 7
8 3
9 8
5 5
7 I
3 5
9 7
6 3
9 8
4 5
6 7
7 7
8 8
2 4
2 5
- 3 4
TOTAL SCORE 112 88 72 72 60 83 67 1" = does not meet quality concepy
'10 = meets quality concepts fully Table 6.1 Ratings of Co.mrmon Chlorine Analytical Methods vs. the "Ideal" MetIod 27
is 9/19/2003 Tm 11:48 A ot Justin-.Peat 6 914402805661 ao 3.3 Page, 032-035 Corany mxifications (DPD colorinetric, DPID titrnmctric, iolometric titration, and forwartl and back aroperomerric titrations). The FACIS method and the iodine electrode method were based on experience with StandanMetxcd) methodologies.
A sliding scale was used in the ratings. On the scale,"lfl Ieans thc method mees the quality concept of the "ideal"mdod completely and"1" mens the method dom not meet the concept at all. Each concept was weighed equally. The ctodis were judSd versus eaci of tlie 14 ideal method concepts and the ratings were tallied. Table 6.1 shows the results of the ratings.
As subjectively idicated in Table 6.1, Hacl's DPD colorimtric method is dcoser to the conceptual "ideal method tlan any of th-e other common chlorine analytical methods. Most of the limitations associated with the traditional DPD demistry (e.g., calibration iicarity, reagent stability; reaction product stability, etc.)
lre been addressed sufficiently in Hach Company's procedures and reagent formulations. Hach versions of the DPD chemistry have been successful in several studies under various conditions.
Althougl the amperometric titration method generally is perceived as the 'referee' method for clorine determinations hi NortlAmerica, it has been shown that several sources of error can occur when using this method unless precautions are taki. Contrary to the notion that the amperometric method is free of most couomnon interferences, several poorly documented interferences have been identified. The ampemmetric metlod requires much greater sIldl to perform and a thornugh. understanding of tle nature of the sample to be tested.
Even with these limitations, in the hands of a skilled operator and withi thorough tnowledge of the sample to be tested, the anmercrnetric procedures can provide accturate and precise data. Because the axrometric methods are not easily adapted to the field, some trade-off in precision and accuracy can be expected due to analyte loss or changes to the sample during the holding period.
In view of the relative instability of chlorine and chloranhes in aqueous solutions arxd the availability of accurate digital titrators, colorimeters and portable spectrophotometers, on-site testing for chlorine is preferable.
Corsidering these iictors and Fladh Com;puiy's versions of the DPD ctemistry, one cai be assured of the most reliable, accurate and precise data available with onasite testing using portable instrumentation. Many would consider this as the 'ideal" system for routine chlorine measurements.
28
i 9/19/2003 Tmet 11t49 AM Tot Ju.stin-Peat 9,1440290561 Paget 033-035
References:
1.1 lcit, G. C; Harndxwok elf Onladnafofn and Alternatix?, DisfItfecats, 3rd cd;%n Nostrand Rcinhold, NewvYodc, 1992 1.2 Hazp, D.L;A Specfic and Effective Meth frfr onbrilling Gbhkraminafian qf)aten-Hadh Comjiy, 200.
1.3 Manual of Wter Cbloriaf kn Prindplie and PradiesArnerican WterXdrksAs soiation, 1973.
1.4 WLasteUater DLInfection, Manual of Practice FD-1 0;%Vater Pollution Control Federation, 1986.
1.5 For a review, see Brungs,W.A.;our Wafer Pllution Contro Fed; 45, 2180 (1973).
2.1 PalinA. T;jmurAm Water WbAsrAz-c; 49, 873 (1957).
2.2 Gordon, G.; Cooper;W; Rice, R; and Pacey, G.;
Divinfectm zt Redd=dMeas-ujtrtnentMethxxL&,
2nd. ed;AWWA iteseaxch oundation andArnerican
'WaterWorksAssociation, 1992, p. 62.
2.3 Stdanl Methodqfb.r the fxaminatm qf Witer and Wasteuxter, 18th ed.,American Public Health Association, American Water brks Association, and Water Envirnonent Federation, 1992, Method 450CI G., p. 4-46.
2.4 "nternationml Organization for Standardization, Water Quality,; ISO Standa 7393-2:1985.
2.5 CooperW; Roscler, N; and Silicer, R *JorAm Wtter Mriks-Aoa; 74; 362 (1982).
2.6 Standadrl Metfbod';for the Examination qf Water and Wateuxitei-, 18th ed.; op. cit., Metlod 450C Ed,
- p. 44 4.
2.7 Sengupta, C; "Survey of Chlorine Analytical Methods Suitable for the Power Industry"; EPRI Report FA-929, October 1978, p. 5.22.
2.8 Harp, D.;"Application of the DPD Calorimetric Methiod for MeasuringTraceotl Residual Clorinc";
Proceedings of the G6hlAnnual Conference and Exsition, Water Environment Federation, paper AC93-059X)2,1993.
2.9 Title 40, Congzr ional Federzl 1egtter Appendix B, Section 136,7-1-94.
2.10 Hatch, G.;Yang,V;jburAm WzterWn1s A.oYXa;75, 154 (1983).
2.11 St andvd Metxodjftr the Examinatfrn qf Water and Wasteuxter 18th ed.; op. cit., Method 4500a D.,
- p. 4-42.
2.12 Standan Method;ftr the Eamrinatmin qf Water and Wasteuxder 18th ed.; op. cit.,Metod 45(XK-a D.,
- p.
4-36 2.13 Gordon, G.; ct aI;Disinfectwnt Resildual McureientMetlxxkd.g op. cit.; p. 15.
2.14 EllmsJ.; HausetS.Ljrour Int Eng. Ghen; 5,915 (1913).
2.15 "Water Chlorine (Residual) No. 1 ";Analytical Reference Service Report No. 35, United States Environmental ProtectionAgency, Glicinnati, Oh1io, 1969.
2.16 "Water Cllorine (Residual) No. 2";Analytical Referencr Service Report No. 4-0, United States Bvironmental ProtectionAgency, Cncinnati, Ohio, 1971.
2.17TomplnsJ.;Tsai C; Tran4 m FiA.ASc; 105, 313 (1976).
2.18 Pavaj.;Tsai, C; Tram:Am Fish &cc; 105,430 (1976).
2.19 Lciberrnnj.; Roscler, N.;.eir, E; and Cooer, W;Evrn..ScY Tech, 14,1395 (1980).
2.20 Standant Metbxod for th>e Examination (f Water and Wasteuxaer, 18th cd.; op. cit., Methd 4500 0 H.,
- p. 4.47.
2.21 Chiswell, B.; OUfiloran, K;Anal Gfii Acta, 248, 519(1991).
2.22 Dimmock, N; Midglcy, D.; Taknta, 29,557 (1982).
2.23 Wilde, E-; Wct Rearsurce; 25,1303 (1991).
3.1 Jolley, R; Brungs,W.; Gotruvo,J.; Cumming, R; Matticej.;Jacos.,V; Water CGlrinat& Envzrmmntl Impact and Health Effect;,Volune 4; Book 1; Chlemistry and WaterTreatment;AnnAtbor Science; 1983; p. 33.
3.2 Cooper,WX/; Sorber, C; Meirer, E Lkur.Am Water 1?,t-sAoc.; 67; 34 (1975).
3.3 Bongrs, L; O'ConnorT.; and Burton, D.;"Bromide Chloride --AnAltenate to Chlorine for Fouling Control in Condenser Cooling Systerns"; EPA GIX)/7-77.053; United States Envirownental ProtectionAgency; 1977.
3.4 Morris,J.; Rarn, N.; Baum, B.;Wajon, E; "Foriration and Silificuce of NCiloro Compounds in Water Supplies"; EPA 500/280031; United States Envimirnental Protection Agency; 1980.
3.5 Wijon, J.; M6rrisj.;Entinrrn International; 3; 41 (1980).
3.6 Mite, G. C, Handx* of Cblornatiom and Alternative Dsinfectnb op. cit.; p. 287.
29
ii 9/19/2003 Times 11s48 AM Too Justin-Peat 9,144028056B1 Page$ 034-03S 3.7 Sengupta, C;"Survey of ChlorineAnalytical Methods Suitable for the Rower Lndustry"; op. cit.; p. 3-9.
3.8 ibid; p. 3-12.
3.9 ibid;p. 3-15.
3.10 Gordon, G.; Sweein, D.; Srnith, K; Pacey G.;
Talma; 38,145 (1991).
3.11 ASTM Dl 193-7:"Standck Specification for Reagnat Wtcr";Annul Book ofAM Standars; Amecricu Society forTeszing asyi Materials; 1994.
3.12 Vogel, A.; A 71vdlxx-)k of Que.n titadixe Inorganic AntaliyL, 3rd ed; Lonnans Publishing; 1961.
3.13 acih Compuy; WiiterAnabdsandrxxjk; 2nd ed.; 19924 Section I.
3.14 Gordon, G;et al.; Diinfectant Residual easurmnent Mcflxci; op. dt.;Thble 2.1(J 3.15 Strupler,N.jlnst WaterEng. anl ScL;39; 134(1985).
- 3. 16')little, G.;"New Methods for tlle Clorimeiric Determination of Halogen Residuals"; PHID.
Dissertation; University of Forid;L 1966.
3.17 Michalis, LjAm Cxen SrxC; 53; 2953 (1931).
3.18Jafari, G.; NuinAj Chem.So; 93,823 (1971).
3.19 Standard MetJ)djfbr tbe Examinatrm rf Water anzd Was-teuxiter, 18th, ed.; op. cit., Method 4500CIA.
3.20 ibid.; Method 4500C Gh.
3.21 ibid.; Method 45X-CIA.
3.22 ibid.; Method 4500C D.b.
3.23 Wlite, G. C, Handbook of Cllorination and Alternative Disinfectats; op. cit.;p. 227.
3.24 Marerurn, D.; Schurter, L; HobsonJ.; Moore, E; Environ. Sci. Tecluol.; 28; 331 (1994).
3.25 WXhite, G.C, Handx~ok qf Chlbrinairm and Alternatire Disinfectant, op. cit.; p. 226 4.1 Gordon, G.; et al.; Disinfecant Resdual Measrment Met~bex: op. cit.; Chap. 2,.Sec.Vm.
4.2 Instrumnitation Testing Service, Inc.;"Evaluation Report, Hach Model 31300 Total Chlorine Purp ColorimeterAnalyzer'; Report 84-3; 1983.
4.3 The Water and Wastewater istrumentation TestingAssodation;"Prfonm-ance Evaluation of Residual CllorineAnalyzcrs forWater and Wastewater TreatmentApplicationls"; Report CH-1; 1990.
5.1 Whrld Health Oaniationl;"Guielinesfor Drlnktng Water Qualt, VL u3:Sm C
nity Supplies";; 1993; Chap. 6.
5.2 U.S. Patent No. 5,362,650; JVra-kwRange alori ne Determina m bIntlmlor Dmnial L Harp; Assignee: Hach Company; Nov. 8,1994.
5.3 Ttle 40, GCngr-ssziYna1 iedeird Regiter, CIL 1, Section 141.74,7-1-92.
6.1 Gordon, G.; et al.; Disinfectant Residual MeasurenwntMetlxx& op. cit.; p.33-35..
Trademarks Thne following are trademnarks of Hadi Compzany:
AccuMacP AutoCitT?
Pocket ColorimeterT 1' TenSette Acknowledgements Tnc author expresses appreciation to tle following, for proofing the rmnuscript and for their ldnd encouragement:
Lee Cooper Mare Hale Starla Harp Tim Holtz Tom Haukebo Bob Klein Sharon Sloat Pat WNrese 30
Leo J. Harte 01/2012004 12:18 PM To: Eric.nygaard@epa.state.oh.us cc:
Subject:
Requested Infromation for Chlorine Analysis RECS-04-00006 Ms. Underwood and Mr. Nygaard, Attached is a link to the instrument technical manual that you requested:
http://vwvw.hach.com/fmmimhach?/CODE:46760883871 A hardcopy or the manual will be sent via mail. The related technical paper has been faxed per you request. Please let me know if you required any additional information.
Thank you, Leo Harte Perry Nuclear Power Plant Environmental Specialist 440-280-5514
46760-88 POCKET COLORIMETERT M Analysis System Chlorine (Cl2)
Instruction Manual C Hach Company, 1991-2001. All rights reserved. Printed in the U.S.A.
te/dk 6/01 8ed
2
TABLE OF CONTENTS CERTIFICATION.......................
5 SAFETY PRECAUTIONS.......................
9 Use of Hazard Information..........................
9 Precautionary Labels..........................
10 SPECIFICATIONS.......................
11 OPERATION........................................................................................................ 13 GENERAL DESCRIPTION.......................
15 Safety Precautions..........................
18 Battery Installation............................................................................................ 18 Operation..........................
20 CALIBRATION..........................
23 User-Entered Calibration..........................
23 Instrument Calibration..........................
25 Exiting the Calibration Routine..........................
30 Retrieving the Factory Calibration..........................
30 ERROR MESSAGE DISPLAY.......................
33 Error Messages..........................
33 3
TABLE OF CONTENTS, continued POCKET COLORIMETERTM INSTRUMENT PROCEDURES..........
37 CHLORINE, FREE................................................ 39 DPD Method......................................................
39 Accuracy Check...................................................... 47 Interferences......................................................
47 CHLORINE, TOTAL, Low Range....................
............................ 51 DPD Method......................................................
51 Accuracy Check...................................................... 60 Interferences......................................................
60 CHLORINE, TOTAL, High Range......................
.......................... 65 DPD Method......................................................
65 Accuracy Check and Interferences..............................
........................ 69 USING SpecVrm SECONDARY STANDARDS............................................ 71 GENERAL INFORMATION................................................ 73 HOW TO ORDER................................................
75 REPAIR SERVICE................................................ 77 WARRANTY................................................
78 4
CERTIFICATION Hach Company certifies this instrument was tested thoroughly, inspected, and found to meet its published specifications when it was shipped from the factory.
The Pocket Colorimeter'm instrument has been tested and is certified as indicated to the following instrumentation standards:
EMC Immunity:
Per 89/336/EEC EMC: EN 61326:1998 (Electrical Equipment for measurement, control and laboratory use-EMC requirements). Supporting test records by Hach Company, certified compliance by Hach Company.
Standard(s) include:
IEC 1000-4-2: 1995 (EN 61000-4-2: 1995) Electro-Static Discharge Immunity (Criteria B)
IEC 1000-4-3:1995 (EN 61000-4-3: 1996) Radiated RF Electro-Magnetic Field Immunity (Criteria A)
Additional Immunity Standard(s) include:
ENV 50204: 1996 Radiated Electro-Magnetic Field from Digital Telephones (Criteria A)
Radio Frequency Emissions:
Per 89/336/EEC EMC: EN 61326: 1998 (Electrical Equipment for measurement, 5
CERTIFICATION, continued control and laboratory use-EMC requirements) "Class B" emission limits.
Supporting test records by Criterion Technology O.A.T.S. (NVLAP #0369), certified compliance by Hach Company.
Additional Radio Frequency Emissions Standard(s) include:
EN 55022 (CISPR 22), Class B emissions limits.
Canadian Interference-causing Equipment Regulation, IECS-003, Class A:
Supporting test records by Criterion Technology, Intellistor O.A.T.S.
(NVLAP #0369), certified compliance by Hach Company.
This Class A digital apparatus meets all requirements of the Canadian Interference-Causing Equipment Regulations.
Cet appareil numerique de la classe A respecte toutes les exigences du Reglement sur le materiel brouilleur du Canada.
FCC Part 15, Class "A" Limits: Supporting test records by Criterion Technology, Intellistor O.A.T.S. (NVLAP #0369), certified compliance by Hach Company.
This device complies with Part 15 of the FCC Rules. Operation is subject to the following two conditions:
(1) This device may not cause harmful interference, and (2) This device must accept any interference received, including interference that may cause undesired operation.
6
CERTIFICATION, continued Changes or modifications to this unit not expressly approved by the party responsible for compliance could void the user's authority to operate the equipment.
This equipment has been tested and found to comply with the limits for a Class A digital device, pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference when the equipment is operated in a commercial environment. This equipment generates, uses, and can radiate radio frequency energy and, if not installed and used in accordance with the instruction manual, may cause harmful interference to radio communications.
Operation of this equipment in a residential area is likely to cause harmful interference, in which case the user will be required to correct the interference at his own expense. The following techniques of reducing the interference problems are applied easily.
- 1. Remove power from the Pocket Colorimeter instrument by removing one of its batteries to verify that it is or is not the source of the interference.
- 2. Move the Pocket Colorimeter instrument away from the device receiving the interference.
- 3. Reposition the receiving antenna for the device receiving the interference.
- 4. Try combinations of the above.
7
8
SAFETY PRECAUTIONS Please read this entire manual before unpacking, setting up, or operating this instrument. Pay particular attention to all danger and caution statements. Failure to do so could result in serious injury to the operator or damage to the equipment.
To ensure the protection provided by this equipment is not impaired, do not use or install this equipment in any manner other than that which is specified in this manual.
Use of Hazard Information If multiple hazards exist, this manual will use the signal word (Danger, Caution, Note) corresponding to the greatest hazard.
DANGER Indicates a potentially or imminently hazardous situation which, if not avoided, could result in death or serious injury.
CAUTION Indicates a potentially hazardous situation that may result in minor or moderate injury.
NOTE Information that requires special emphasis.
9
SAFETY PRECAUTIONS, continued Precautionary Labels Please pay particular attention to labels and tags attached to the instrument.
Personal injury or damage to the instrument could occur if not observed.
A This symbol, if noted on the instrument, references the instruction manual for operational and/or safety information.
10
SPECIFICATIONS Lamp: Light emitting diode Detector: Silicon cell Wavelength: 528 nm Accuracy: +/- 0.02 mg/L at 25 C Repeatability: 0.01 mg/L Filter bandwidth: 15 nm Absorbance range: 0 to A Dimensions: 3.2 x 6.1 x 15.2 cm (1.25 x 2.4 x 6 inches)
Weight: 0.2 Kg (0.43 lbs)
Operating conditions: 0 to 50 C; 0 to 90% relative humidity (noncondensing)
Sample cell pathlength: 10 and 22.35 mm Power supply: 4 AAA alkaline batteries; approximate life is 750 tests 11
12
OPERATION DANGER Handling chemical samples, standards, and reagents can be dangerous. Review the necessary Material Safety Data Sheets and become familiar with all safety procedures before handling any chemicals.
DANGER La manipulation des echantillons chimiques, etalons et ractifs peut ere dangereuse. Lire les Fiches de Donnees de Securite des Produits (FDSP) et se familiariser avec toutes les procedures de scurite avant de manipuler tous les produits chimiques.
PELIGRO La manipulaci6n de muestras quimicas, estandares y reactivos puede ser peligrosa. Revise las fichas de seguridad de materiales y familiaricese con los procedimientos de seguridad antes de manipular productos quimicos.
GEFAHR Das Arbeiten mit chemischen Proben, Standards und Reagenzien ist mit Gefahren verbunden.
Es wird dem Benutzer dieser Produkte empfohlen, sich vor der Arbeit mit sicheren Verfahrensweisen und dem richtigen Gebrauch der Chemikalien vertraut zu machen und alle entsprechenden Materialsicherheitsdatenblatter aufmerksam zu lesen.
PERIGO A manipulacao de amostras, padroes e reagentes quimicos pode ser perigosa. Reveja a folha dos dados de seguranga do material e familiarize-se com todos os procedimentos de seguranga antes de manipular quaisquer produtos quimicos.
PERICOLO La manipolazione di campioni, standard e reattivi chimici pub essere pericolosa. La preghiamo di prendere conoscenza delle Schede Techniche necessarie legate alla Sicurezza dei Materiali e di abituarsi con tutte le procedure di sicurezza prima di manipolare ogni prodotto chimico.
13
14
GENERAL DESCRIPTION Hach Pocket Colorimeterm instruments* are low-cost, high-quality filter photometers designed for single wavelength colorimetric measurement. This model is calibrated to measure free or total chlorine content (depending on the indicator reagent used) in water samples from 0 to 2.00 mgAL with the 1-inch sample cell and 0 to 4.5 mg/L with the 1-cm/10-mL sample cell and adapter. The liquid crystal display provides a direct readout in milligrams per liter chlorine. The factory calibration can be over-ridden with an operator-entered two-point calibration if desired.
The operator calibration will remain in memory until the operator performs a series of keystrokes that will restore the factory calibration.
Power is supplied by four AAA alkaline batteries. Typically, a set of batteries provides approximately 750 tests because of battery-saving features incorporated in the software. The instrument will automatically shut off if no keystrokes are made for one minute when in the measurement mode or 10 minutes when in the calibration mode. The colorimeter lamp is an LED and is on only long enough for the measurement sequence to take place (approximately 2 seconds).
- U.S. patents 5,083,868 and D333,992.
15
GENERAL DESCRIPTION, continued The instrument comes with 2 10-mL sample cells, two 1-cm/10-mL sample cells, enough DPD Reagent Powder Pillows for 100 free and 100 total chlorine tests, four AAA batteries and this instruction manual contained in a 22.5 x 17.5 x 145 cm (9 x 7 x 6 inch) polypropylene case.
16
GENERAL DESCRIPTION, continued Figure 1 Chlorine Pocket ColorimeterTM Packaging Guide
.3
.2 21
- 1. Pocket Colorimeter Tm Instrument, Chlorine.................................... 46700-00
- 2.
Caps, Sample Cell, 1-cm/1 0-mL (under instrument)..................... 52626-00
- 3.
DPD Free Chlorine Powder Pillows.....................................
21055-49
- 4.
Sample Cells,1 -cm/1 0-mL.....................................
41658-00
- 5. Sample Cells, 1 0-mL with caps.....................................
24276-06
- 6. DPD Total Chlorine Powder Pillows.....................................
21056-49
- 7.
Batteries, Alkaline MA, 1.5 V, 4/pkg.....................................
46743-00 17
GENERAL DESCRIPTION, continued Safety Precautions As part of good laboratory practice, please familiarize yourself with the reagents used in these procedures. Read all product labels and the material safety data sheets (MSDS) before using them. It is always good practice to wear safety glasses when handling chemicals. Follow instructions carefully. Rinse thoroughly if contact occurs. If you have questions about reagents or procedures, please contact Hach.
Battery Installation Figure 2 provides an exploded view of battery installation. Loosen the captive screw and remove the battery compartment cover. The proper polarities are shown on the battery holder. Place the four batteries provided with the instrument in the holder as indicated and replace the battery compartment cover. The display will show the software version number (e.g., P 1.6) after correct battery installation.
When replacing discharged batteries, always replace the complete set of four.
Rechargeable batteries are not recommended and cannot be recharged in the instrument.
18
GENERAL DESCRIPTION, continued Figure 2 Battery Installation I
I I
I
~~~~~~~~~~~~~~~~~~~~~~~~~~~I I
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~I I ~
~
~
I I
I I
I I
19
GENERAL DESCRIPTION, continued Operation All instrument functions are performed using two keys and the digital display. For the normal operation of measuring the concentration of chlorine in the sample solution, a simple, five-step procedure is performed as follows. This is a general procedure.
When measuring actual samples for chlorine, follow the more detailed procedure on page 40 for free chlorine, page 52 for low range total chlorine or page 66 for high range total chlorine.
- 1. Fill a clean sample cell to the 10-mL mark with the blank solution (usually untreated sample). Fill another clean sample cell to the 10-mL mark with sample.
- 2. Add the contents of one pillow of the appropriate DPD chlorine reagent to the cell containing the sample. Cap and shake the cell for 20 seconds. This is the prepared sample.
- 3. Place the blank in the cell compartment. Cover the sample cell with the instrument cap as shown in Figure 3.
Note: When using the instrument cap as a light shield during measurements, place the cap with the curved surfade toward the keypad. This position will allow the cap to match the grooves in the instrument case to provide a good seal against stray light.
20
GENERAL DESCRIPTION, continued
- 4. Press the ZERO key. After approximately 2 seconds, the display will read: 0.00.
- 5. Place the sample cell containing the prepared sample into the cell holder and cover with the instrument cap. Press the READ key. After approximately 2 seconds, the display will indicate the chlorine concentration in milligrams per liter (mgAL). For example: 1.15 on the display means 1.15 mg/L as C12.
Note: For accurate readings, make sure sample cells are wiped free of liquid or fingerprints.
Any liquid entering the sample cell compartment can damage the instrument.
Figure 3 Sample Cell Insertion
[Tro 21
22
CALIBRATION The Pocket Colorimeterm instrument is factory-calibrated to save you the time and expense required to construct your own calibration curve. It is ready for use without calibration by the user. See Using SpecVm Secondary Standards on page 71 to verify consistent instrument operation.
The instrument also will accept a user calibration if your regulatory official or agency requests that you use one. The following calibration section will show you how to perform your own calibration to meet these regulatory requests. Using the factory calibration, however, is generally recommended when permitted.
User-Entered Calibration The instrument accepts two user-entered, two-point calibrations. One calibration is for the 0 to 4.5 mgAL (high range) total chlorine test. The other calibration is for the 0 to 2.00 mg/L free chlorine and total chlorine tests.
To perform a user-entered calibration, make a chlorine standard solution (a sample of known chlorine concentration can be used). Use DPD reagents to develop the color in the standard or the sample. (The chlorine concentration must be between 1.60 to 2.00 mg/L C12.) Then the concentration of the prepared chlorine standard or sample must 23
CALIBRATION, continued be determined with an alternate laboratory instrument such as a spectrophotometer, colorimeter, or by amperometric titration.
By testing a standard before calibration, you can calculate the difference between the instrument's readings and the expected values. This difference will indicate the shift in results for comparable samples after the calibration is performed.
Preparing a Chlorine Calibration Standard Solution
- 1. Snap the neck off a Chlorine Standard Solution Voluette Ampule.
- 2. Pipet 2.00 mL of chlorine standard from the Voluette Ampule into a 1 00-ml graduated cylinder.
- 3. Use the following formula to calculate the final volume of the diluted chlorine standard:
1.11 x concentration of chlorine standard in Voluette ampule = final volume (mL)
- 4. Using chlorine demand-free water, dilute the 2.00 mL of chlorine standard transferred to the graduated cylinder to the final volume calculated in step 3. This is the chlorine standard working solution. Use this solution for calibration immediately-the chlorine concentration will decrease with time.
24
CALIBRATION, continued This procedure should produce a final chlorine concentration of approximately 1.8 mg/L C12. Due to possible chlorine demand in the dilution water and other factors, the concentration may actually be higher or lower. Because of the potential difference between the theoretical and actual chlorine concentration, it will be necessary to determine the chlorine concentration of the working chlorine standard with an alternate instrument or method. You can use the standard as long as the chlorine concentration is between 1.60 to 2.00 mg/L C12.
Instrument Calibration
- 1. Begin calibrating the Pocket Colorimeter instrument by ensuring it is in the correct range you wish to calibrate. To determine which range the instrument is in, press the ZERO or READ key and look at the display. The low range mode display will show 0.01 mg/L C12 resolution. The high range mode display will show 0.1 mg/L C12 resolution. The low range mode is used to calibrate the 0 to 2.00 mgAL free chlorine and total Chlorine tests. The high range mode is used to calibrate the 0 to 4.5 mgAL total chlorine test. To change modes, press both the ZERO and READ keys simultaneously. After one second, release the ZERO key and hold the READ key until HI or LO appears in the display. Repeat until the 25
CALIBRATION, continued instrument displays the desired mode. Release the key when the instrument is in the correct mode.
- 2. Press both the ZERO and READ keys simultaneously and hold them down for two seconds. The display will show CAL, followed by a flashing 0.
- 3. Insert the blank (chlorine demand-free water) into the cell holder. Cover the sample cell with the instrument cap.
Note: Wipe all liquids off the sample cell. Any liquid entering the sample cell compartment can damage the instrument.
- 4. Press the ZERO key. The instrument will display --- followed by 1.60.
- 5. Follow the appropriate colorimetric procedure to develop the color in 10 mL of the working standard solution. This is the prepared chlorine standard solution.
- 6. Using 10-mL sample cells, measure the prepared chlorine standard solution concentration against a blank with a different instrument. The DR/2000, DR/2010, DR/3000 and DR/4000 will need the AccuVac adapter inserted into the cell holder to use the I 0-mL round cell.
26
CALIBRATION, continued If you use amperometric titration, two aliquots of diluted chlorine standard are necessary. Develop the color in one 10-mL aliquot using the DPD chlorine reagents. Titrate the second aliquot using amperometric determination of the chlorine concentration. Use the concentration of the chlorine standard determined amperometrically along with the standard developed with DPD for instrument calibration.
If the prepared chlorine standard concentration is outside the range of 1.60 to 2.00 mg/L C12 (1.6 to 2.0 mgfL for high range), make another dilution of the standard. Adjust the volume of the standard by the appropriate amount so the diluted chlorine standard falls within the specified range.
Note: The following steps must be done quickly to prevent changes in the chlorine concentration that may affect calibration accuracy.
- 7. Press the ZERO or READ key to change (by scrolling up) the displayed 1.60 (1.6 for high range) to the concentration value determined for the prepared chlorine standard solution. If you scroll up past the value, keep scrolling. The display will "wrap around" to 1.60 again. Pressing the READ key increases the display by hundredths, pressing the ZERO key increases the display by tenths.
27
CALIBRATION, continued
- 8. Press both the ZERO and READ keys simultaneously and hold them until Std appears in the display.
- 9. For the high range calibration only, transfer at least 1 mL of the reacted chlorine standard solution from the 10-mL cell to a 1-cm/10-mL sample cell.
For the low range calibration, use the 10-mL sample cell.
Insert the reacted chlorine standard solution into the cell holder. Cover the sample cell with the instrument cap.
- 10. Press the READ key. The instrument will compute the calibration and then display the value entered for the standard.
- 11. The calibration is complete. The instrument will use this calibration to determine the displayed concentration for future sample measurements. To exit from the calibration routine or return to the factory calibration, follow the instructions on page 30.
28
CALIBRATION, continued Calibration Quick Reference Step Keystroke Display
- 1. Turn power on.
READ
--- then a number
- 2. Determine if in high or low range ZERO X.XX for low range, mode.
X.X for high range
- 3. Select desired range mode.
ZERO & READ Hi or LO hold READ
- 4. Select calibration mode.
ZERO & READ CAL, then flashing 0
- 5. Place blank into cell holder.
ZERO
--- then 1.60 or 1.6
- 6. Determine standard concentration by other means.
- 7. Immediately scroll to concentration ZERO or READ 1.60 then scrolls up with value.
keystroke
- 8. Enter standard concentration value.
ZERO & READ Std
- 9. Place standard in cell holder.
READ Shows standard Instrument exits calibration mode.
concentration.
To exit in middle of calibration mode:
ZERO & READ Std ZERO& READ ESC 29
CALIBRATION, continued Exiting the Calibration Routine When the display flashes 0, or when Std appears in the display, exit the calibration routine by pressing both the ZERO and READ keys simultaneously and hold them for two seconds. The instrument exits to normal mode and ESC will appear and remain displayed until ZERO or READ is pressed (this also performs the function of the pressed key) or until automatic shut-off occurs. The instrument uses the last completed user-entered calibration or the factory calibration if no user-entered calibration has been completed to determine sample chlorine concentrations.
To exit when 0 or Std are not displayed, press both keys until Std is displayed, then press both keys to exit. Or, let the instrument sit 10 minutes until it automatically shuts off.
Retrieving the Factory Calibration
- 1. If you have entered both a low and high range user-entered calibration, be sure the instrument is in the same range mode as the range you want to retrieve. To retrieve a low range factory calibration, the instrument must be in the low range mode. See step 1 of Instrument Calibration to determine which mode the instrument is in.
30
CALIBRATION, continued
- 2. To retrieve the factory calibration, press both the ZERO and READ keys simultaneously and hold them for three seconds. CAL will appear in the display, followed by a flashing 0.
- 3. While the display is flashing, press and hold the READ key for two seconds. The display will show dFL and the calibration mode is exited. dFL is displayed until the ZERO or READ key is pressed (which also performs the function of the pressed key) or until automatic shut-off occurs. The instrument will use the factory calibration to determine chlorine concentrations of measured samples.
31
32
ERROR MESSAGE DISPLAY When the instrument cannot perform the function initiated by the operator, an error message will appear in the display. Refer to the appropriate message information below to determine what the problem is and how it can be corrected. Resolve error messages in the order that they appear on the display. Hach Service Centers are listed on page 77.
Error Messages
- 1. E-1 Unstable Reading Verify instrument cap is correctly seated.
Check for light blockage.
Verify LED lights up when a key is pressed.
Contact a Hach Service Center.
- 2. E-2 Low Light Error Check for light blockage.
Verify LED lights up when a key is pressed.
Contact a Hach Service Center.
33
ERROR MESSAGE DISPLAY, continued
- 3. E-3 Low Battery Message Verify batteries are installed properly.
Replace batteries.
Contact a Hach Service Center.
- 4. E-4 EEPROM failure Verify low battery message (E-3) is not displayed before E-4.
Contact a Hach Service Center.
- 5. E-5 EEPROM failure on zeroing function Verify low battery message (E-3) is not displayed before E-5.
Contact a Hach Service Center.
- 6. E-6 EEPROM failure on calibration Verify low battery message (E-3) is not displayed before E-6.
Contact a Hach Service Center.
34
ERROR MESSAGE DISPLAY, continued
- 7. E-7 Improper calibration Verify instrument cap is correctly seated.
Check for light blockage.
Verify LED lights when a key is pressed.
Verify chlorine standard was measured after zeroing.
Contact a Hach Service Center.
- 8. Flashing 0.00 (underrange)
Verify instrument cap is correctly seated.
Check zero by reading a blank. If error recurs, re-zero the instrument.
Contact a Hach Service Center.
- 9. Flashing 2.20 (overrange in LO range)
Overrange - dilute and re-measure the sample.
Check for light blockage.
- 10. Flashing 5.0 (overrange in HI range)
Overrange - dilute and re-measure the sample.
Check for light blockage.
35
36
POCKET COLORIMETERTM INSTRUMENT PROCEDURES Before testing, make sure the instrument is in the correct range mode. For the 0 to 2.00 mg/L free and low range total chlorine tests, the instrument should be in the low (LO) range mode. The display will read to hundredths (0.00).
For the high range total chlorine test, the instrument should be in the high (HI) range mode. The display will show tenths (0.0).
To access the alternative range mode, press both the ZERO and READ keys simultaneously. After one second, release the ZERO key and continue to hold the READ key until the letters HI or LO appears in the display. These letters designate the calibration range the instrument will use to determine chlorine in samples.
37
38
Method 8021 CHLORINE, FREE ( to 2.00 mg/L Cl2)
For water, wastewater and seawater DPD Method* USEPA accepted for reporting" Measuring Hints If the sample temporarily turns yellow after reagent addition, or the display shows overrange (flashing 2.20 in display), dilute a fresh sample and repeat the test. A slight loss of chlorine may occur because of the dilution. Multiply the result by the appropriate dilution factor.
- Adapted from Standard Methods for the Examination of Water and Wastewater.
- I Procedure is equivalent to USEPA method 330.5 for wastewater and Standard Method 4500-Cl G for drinking water.
39
CHLORINE, FREE, continued
- 1'
.11 4
- 4V~~~~
4
'I;
- 1. Fill a 10-mL cell to the 10-mL line with sample (the blank). Cap.
Note: Samples must be analyzed immediately and cannot be preserved for later analysis.
Note: Be sure the instrument is in the low range mode. See page 37.
- 2. Remove the instrument cap.
Note: For best results, zero the instrument and read the sample under the same lighting conditions.
- 3. Place the blank in the cell holder with the diamond mark facing you.
Tightly cover the cell with the instrument cap (flat side should face the back of the instrument).
Note: Wipe liquid off sample cells.
40
7 CHLORINE, FREE, continued I1 k_.V o4*
SS-I ZERO)
.1 a,
i
- ~
- o;__ri xov~f ~a--;-~ I
_4
,,,a,,
- iIS
,>;E, j~~~~~~~~~~~~~*
I
- 4. Press: ZERO The instrument will turn on and the display will show
--- then 0.00.
Note: The instrument automatically shuts off after one minute and the last zero is stored in memory. Press READ to complete the analysis.
- 5. Remove the cell from the cell holder.
- 6. Fill a 10-mnL cell to the 10-mL line with sample.
41
CHLORINE, FREE, continued
- 1
~~~~~~~~~;'l~~~~~~~~~~~~~~~~~~~~I
- 1~~~~~~~~~~~~~~~~~~~~
.'r1
-.t 11 I...
Isis.MIFF wow_
tw1aK.6n
^sws~wvrz K
,id *e n-o..J ;*5*'
- 7. Add the contents of one DPD Free Chlorine Powder Pillow to the sample cell (the prepared sample). Cap and shake gently for 20 seconds.
Note: Accuracy is not affected by undissolved powder.
Note: Shaking dissipates bubbles that may form in samples with dissolved gases.
- 8. Within 1 minute after adding DPD to the sample, place the prepared sample in the cell holder.
Note: A pink color will develop if chlorine is present.
Note: Wipe liquid off sample cells or damage to the instrument may occur.
- 9. Tightly cover the cell with the instrument cap (flat side should face the back of the instrument).
42
CHLORINE, FREE, continued
- 10. Press: READ The instrument will show
- - - followed by the results in mg/L free chlorine.
Note: If the sample temporarily turns yellow after reagent addition, or shows overrange (flashing 2.20), dilute a fresh sample and repeat the test.
43
CHLORINE, FREE, continued Using AccuVac Ampuls I'I
.4~~~~~~~~~~~~~~~~~~~1 I~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
I
- -
1,
-I
'ii '4k i;
'i11 j".-,_
I II
- 1. Fill a 10-mL sample cell to the I 0-mL line with sample (the blank). Cap.
Collect at least 40 mL of sample in a 50-mL beaker.
Note: Samples must be analyzed immediately and cannot be preserved for later analysis.
- 2. Remove the instrument cap.
Note: For best results, zero the instrument and read the sample under the same lighting conditions.
Note: Be sure the instrument is in the low range mode. See page 37.
- 3. Place the blank in the cell holder, with the diamond mark facing you.
Tightly cover the cell with the instrument cap (flat side should face the back of the instrument).
Note: Wipe liquid off sample cells.
44
CHLORINE, FREE, continued
1 J ZERO H
1 A
.1 A
.1K ill~~~~~~
<->1 SI
; -J I
- 4. Press: ZERO The instrument will turn on and the display will show
--- then 0.00.
Note: The instrument automatically shuts off after 1 minute and stores the last zero in memory. Press READ to complete the analysis.
- 5. Fill a DPD Free Chlorine Reagent AccuVac Ampul with sample.
Note: Keep the tip immersed until the ampule fills completely.
- 6. Quickly invert the ampule several times to mix. Wipe off any liquid or fingerprints.
Note: A pink color will form if chlorine is present.
Note: Accuracy is not affected by undissolved powder 45
CHLORINE, FREE, continued IT,*
r
~
I;~~~~~~~~~~~~~
ii t;I...
4 I
.,,.z.,,.s,~-,
.. 1 _- t~.,
I.:Jo H)
S i
READ I]
A=~~~~~~~~~~~~~~~~~
- 7. Within 1 minute after filling the AccuVac Ampul, place the prepared sample in the cell holder.
- 8. Cover the ampule with the instrument cap.
Note: Wipe liquid off the AccuVac Ampul.
- 9. Press READ. The instrument will show - - -
followed by the results in mg/L free chlorine.
Note: If the sample temporarily turns yellow after reagent addition or shows overrange (flashing 2.20), dilute a fresh sample and repeat the test. A slight loss of chlorine may occur. Multiply the result by the dilution factor.
46
CHLORINE, FREE, continued Accuracy Check Standard Additions Method
- a. Snap the neck off a Chlorine Standard Solution Voluette Ampule.
- b. Use a TenSette pipet to add 0.1, 0.2, and 0.3 mL of standard to three 25-mL samples. Swirl gently to mix. (For AccuVac Ampuls, use 50-mnL beakers.)
- c. Analyze a 10-mL aliquot of each sample as described in the procedure. Each 0.1 mL of standard will cause an incremental increase in chlorine, the exact value depends on the concentration of the Voluette ampule standard. Check the certificate enclosed with the Voluette ampules for this value.
- d. If these increases do not occur, call Hach at 800-227-4224. Outside the United States, contact the Hach office or distributor serving you.
Interferences Samples containing more the 250 mg/L alkalinity or 150 mgAL acidity as CaCO3 may inhibit full color development, or the color may fade instantly. Neutralize these samples to pH 6-7 with 1 N Sulfuric Acid or 1 N Sodium Hydroxide. Determine the 47
CHLORINE, FREE, continued amount required on a separate 10-mL sample. Add the same amount to the sample to be tested. Correct for the additional volume.
Samples containing monochloramine will cause a gradual drift to higher chlorine readings. When read within one minute of reagent addition, 3.0 mg/L monochloramine will cause an increase of less than 0.1 mg/L in the free chlorine reading.
Bromine, iodine, ozone, and oxidized forms of manganese and chromium may also react and read as chlorine.
To compensate for the effects of manganese (Mn4+) or chromium (Cr6+), adjust the pH to 6-7 as described above. To a 25-mL sample, add 3 drops of 30 g/L Potassium Iodide Solution, mix, and wait one minute. Add 3 drops of 5 g/L Sodium Arsenite and mix. If chromium is present, allow exactly the same reaction period with DPD for both analyses. Subtract the result of this test from the original analysis to obtain the accurate chlorine concentration.
DPD Free Chlorine Reagent Powder Pillows and AccuVac Ampuls contain a buffer formulation that withstands high levels (at least 1000 mg/L) of hardness without interference.
48
CHLORINE, FREE, continued REQUIRED REAGENTS Description Unit Cat. No.
DPD Free Chlorine Reagent Powder Pillows.......................... 100/pkg....
21055-69 or DPD Free Chlorine Reagent AccuVac Ampuls........................
25/pkg........
25020-25 REQUIRED APPARATUS (AccuVac Ampuls)
Beaker, 50 mL..................................
each.500-41 OPTIONAL REAGENTS Chlorine Standard Solution, Voluette Ampules, 50-75 mg/L, 10 mL................................................................ 16/pkg........
14268-10 Chlorine Standard, secondary, Spec/m, 0.0, 0.2,0.8 and 1.5 mgL...................................
4/pkg.
26353-00 DPD Free Chlorine Reagent w/dispensing cap...................... 250 tests.
21055-29 Potassium Iodide Solution, 30 g/L.............................
100 mL MDB*.........
343-32 Sodium Arsenite Solution, 5 g/L.............................
100 mL MDB......... 1047-32 Sodium Hydroxide Standard Solution, 1 N.................... 100 mL MDB......... 1045-32 Sulfuric Acid Standard Solution, I N............................. 100 mL MDB......... 1270-32 Water, deionized..............................
4 L......... 272-56
- Marked Dropper Bottle 49
CHLORINE, FREE, continued OPTIONAL APPARATUS Description Unit Cat. No.
AccuVac Snapper Kit.....................................
each...
24052-00 Batteries, AAA, alkaline.....................................
4/pkg...
46743-00 Caps for 0-mL sample cells.....................................
12/pkg...
24018-12 Cylinder, graduated, 25 mL, poly.....................................
each...
1081-40 Cylinder, graduated, 100 mL, PMP.
..................................... each...
2172-42 sensiOflTml Basic Portable pH Meter, with electrode.................. each...
51700-10 Pipet, TenSette, 0.1 to 1.0 mL......................................
each...
19700-01 Pipet Tips, For 19700-01 TenSette Pipet................................. 50/pkg...
21856-96 Sample Cells, 10-mL with screw caps.....................................
6/pkg...
24276-06 REPLACEMENT PARTS Instrument Cap/light shield............................................................ each......... 46704-00 Instrument Manual.....................................
each...
46760-88 50
Method 8167 CHLORINE, TOTAL, Low Range ( to 2.00 mg/L C12)
For water, wastewater and seawater DPD Method* USEPA accepted (powder pillows only)**
Measuring Hints If the sample temporarily turns yellow after reagent addition or the display shows overrange (flashing 2.20 in display), dilute a fresh sample and repeat the test. A slight loss of chlorine may occur because of the dilution. Multiply the result by the appropriate dilution factor.
- Adapted from Standard Methods for the Examination of Water and Wastewater.
- Procedure is equivalent to USEPA method 330.5 for wastewater and Standard Method 4500-Cl G for drinking water.
51
CHLORINE, TOTAL, Low Range, continued j
4
'4 JsI nnallnnl U-rU-1UL1
- 1. Fill a 10-mL cell to the 10-mL line with sample.
Cap.
Note: Samples must be analyzed immediately and cannot be preserved for later analysis.
Note: Be sure the instrument is in the low range mode. See page 37.
- 2. Add the contents of one DPD Total Chlorine Powder Pillow to the sample cell (the prepared sample). Cap and gently shake for 20 seconds.
Note: Gently shaking dissipates bubbles which may form in samples containing dissolved gases.
- 3. Wait 3 minutes. During this period, proceed with steps 4-8.
Note: A pink color will form if chlorine is present.
Note: Accuracy is not affected by undissolved powder 52
CHLORINE, TOTAL, Low Range, continued
'1
'I
-'
3'
.3
- 4. Fill a 10-mL sample cell to the 10-mL line with sample (the blank). Cap.
- 5. Remove the instrument cap.
Note: For best results, zero the instrument and read the sample under the same lighting conditions.
- 6. Place the blank in the cell holder, with the diamond mark facing you.
Tightly cover the cell with the instrument cap (flat side should face the back of the instrument).
Note: Wipe liquid off sample cells.
53
CHLORINE, TOTAL, Low Range, continued
- 7. Press: ZERO The instrument will turn on and the display will show
- - - followed by 0.00.
Note: The instrument automatically shuts off after 1 minute and stores the last zero in memory. Press READ to complete the analysis.
- 8. Remove the cell from the cell holder.
- 9. Within 3 minutes after the 3-minute reaction period, place the prepared sample in the cell holder.
Note: Wipe liquid off sample cells.
54
CHLORINE, TOTAL, Low Range, continued Ij g :E(; g~~~~~~~~
- 10. Cover the cell with instrument cap.
- 11. Press: READ The instrument will show
--- followed by the result in mg/L total chlorine.
Note: If the sample temporarily turns yellow after reagent addition or shows overrange (flashing 2.20), dilute a fresh sample and repeat the test.
Some loss of chlorine may occur. Multiply the result by the dilution factor.
55
CHLORINE, TOTAL, Low Range, continued Using AccuVac Ampuls uAASze
...t..-.
- . - as.^.::..... vb I I.- -- -- -s-L-.:! -iw -.......................
jrt I
;q"I I. r--)
p I
III
- 1. Fill a 10-mL sample cell to the 10-mL line with sample (the blank). Cap.
Collect at least 40 mL of sample in a 50-mL beaker.
Note: Samples must be analyzed immediately and cannot be preserved for later analysis.
- 2. Fill a DPD Total Chlorine Reagent AccuVac Ampul with sample (the prepared sample).
Note: Keep the tip immersed until the ampule fills completely Note: Be sure the instrument is in low range. See page 37.
- 3. Quickly invert the ampule several times to mix. Wipe off any liquid or fingerprints.
Note: A pink color will develop if chlorine is present.
Note: Accuracy is not affected by undissolved powder.
56
CHLORINE, TOTAL, Low Range, continued Inn n Lynn L
4
'J..
,x SS
'I
- .~ '
-L,,,-11--A
- 4. Wait 3 minutes. During this period, proceed with steps 5-8.
- 5. Remove the instrument cap.
Note: For best results, zero and read the sample measurements under the same lighting conditions.
- 6. Place the blank in the cell holder with the diamond mark facing you.
Tightly cover the cell with the instrument cap (flat side should face the back of the instrument).
Note: Wipe liquid off sample cells.
57
CHLORINE, TOTAL, Low Range, continued
.1~~~~~~~~~~~~~1 1
U~~~~~~~~~~~~~~~~~~~~~~~~~~~~f I
~~~~~~~~~~~~~~~~
1
- 7. Press: ZERO The instrument will turn on and the display will show
--- then 0.00.
Note: The instrument automatically shuts off after 1 minute and stores the last zero in memory Press READ to complete the analysis.
- 8. Within 3 minutes after the 3-minute reaction period, place the prepared sample in the cell holder.
Note: Wipe liquid off sample cells.
- 9. Cover the ampule with the instrument cap.
58
CHLORINE, TOTAL, Low Range, continued
- 10. Press: READ The instrument will show
--- followed by the result in mg/L total chlorine.
Note: If the sample temporarily turns yellow after reagent addition or shows overrange (flashing 2.20), dilute a fresh sample and repeat the test.
Some loss of chlorine may occur. Multiply the result by the dilution factor.
59
CHLORINE, TOTAL, Low Range, continued Accuracy Check Standard Additions Method
- a. Snap the neck off a Chlorine Standard Solution Voluette Ampule.
- b. Use a TenSette pipet to add 0.1, 0.2, and 0.3 mL of standard to three 25-mL samples. Swirl gently to mix. (For AccuVac Ampuls, use 50-mL beakers.)
- c. Analyze a 10-mL aliquot of each sample as described in the procedure. Each 0.1 mL of standard will cause an incremental increase in chlorine, the exact value depends on the concentration of the Voluette ampule standard. Check the certificate enclosed with the Voluette ampules for this value.
- d. If these increases do not occur, call Hach at 800-227-4224. Outside the United States, contact the Hach office or distributor serving you.
Interferences Samples containing more than the 250 mgAL alkalinity or 150 mg/L acidity as CaCO3 may inhibit full color development, or the color may fade instantly. Neutralize these samples to pH 6-7 with 1 N Sulfuric Acid or 1 N Sodium Hydroxide. Determine the 60
CHLORINE, TOTAL, Low Range, continued amount required on a separate 10-mL sample. Add the same amount to the sample to be tested. Correct for the additional volume.
Bromine, iodine, ozone and oxidized forms of manganese and chromium may also react and read as chlorine.
To compensate for the effects of manganese (Mn4+) or chromium (Cr6+), adjust the pH to 6-7 as described above. To a 25-mL sample, add 3 drops of 30 g/L Potassium Iodide Solution, mix, and wait one minute. Add 3 drops of 5 g/L Sodium Arsenite and mix. If chromium is present, allow exactly the same reaction period with DPD for both analyses. Subtract the result of this test from the original analysis to obtain the accurate chlorine concentration.
DPD Total Chlorine Reagent Powder Pillows and AccuVac Ampuls contain a buffer formulation that withstands high levels (at least 1000 mg/L) of hardness without interference.
61
CHLORINE, TOTAL, Low Range, continued REQUIRED REAGENTS Description Unit Cat. No.
DPD Total Chlorine Reagent Powder Pillows.
100/pkg......... 21056-69 or DPD Total Chlorine Reagent AccuVac Ampuls...................
25/pkg......... 25030-25 REQUIRED APPARATUS (AccuVac Ampuls)
Beaker, 50 mL................................................................................
5001each 500-41 OPTIONAL REAGENTS Chlorine Standard Solution Voluette Ampules, 50-75 mg/L, 10 mL
.............................. 16/pkg......... 14268-10 Chlorine Standards, secondary, Spec/T, 0.0, 0.2, 0.8, and 1.5 mg/L 4/set......... 26353-00 DPD Total Chlorine Reagent w/dispensing cap..................
250 tests......... 21056-29 Potassium Iodide Solution, 30 g/L................................. 100 mL MDB*.........
343-32 Sodium Arsenite Solution, 5 g/L.................................. 100 mL MDB.........
1047-32 Sodium Hydroxide Standard Solution, 1 N.................... 100 mL MDB.........
1045-32 Sulfuric Acid Standard Solution, 1 N.............................. 100 mL MDB.........
1270-32 Water, deionized...................................
4 L......... 272-56
- Marked Dropper Bottle 62
CHLORINE, TOTAL, Low Range, continued OPTIONAL APPARATUS Description Unit Cat. No.
AccuVac Snapper Kit.....................................
each...
24052-00 Batteries, AAA, alkaline.............................................................. 4/pkg...
46743-00 Caps for 10-mL sample cells..................................................... 12/pkg...
24018-12 Cylinder, graduated, 25 mL, poly.....................................
each
... 1081-40 Cylinder, graduated, 100 mL, PMP.....................................
each...
2172-42 sensiOtrlml Basic Portable pH Meter, with electrode................. each...
51700-10 Pipet, TenSette, 0.1 to 1.0 mL..................................................... each...
19700-01 Pipet Tips, For 19700-01 TenSette.....................................
50/pkg...
21856-96 Sample Cells, 10-mL with screw caps.....................................
6/pkg...
24276-06 REPLACEMENT PARTS Instrument Cap/light shield..................................... each...
46704-00 Instrument Manual.....................................
each...
46760-88 63
64
Method 8167 CHLORINE, TOTAL, High Range ( to 4.5 mg/L C12)
For water, wastewater and seawater DPD Method* USEPA accepted"*
Measuring Hints If the sample temporarily turns yellow after reagent addition or the display shows overrange (flashing 5.0 in display), dilute a fresh sample and repeat the test. A slight loss of chlorine may occur because of the dilution. Multiply the result by the appropriate dilution factor.
- Adapted from Standard Methods for the Examination of Water and Wastewater.
- Procedure is equivalent to USEPA method 330.5 for wastewater and Standard Method 4500-Cl G for drinking water.
65
CHLORINE, TOTAL, High Range, continued I
_0.
1-i I-t.
~
7r En= t: :N'T.:,;..b+
East Star.~~~~~~~11
- 1. Fill a 1-cm/10-mL cell to the 10-mL line with sample.
Note: Samples must be analyzed immediately and cannot be preserved for later analysis.
Note: Be sure the instrument is in the high range mode. See page 37.
- 5.
.';,,^
}
+.t
^,,,X
,r IfF
- 2. Add the contents of two DPD Total Chlorine Powder Pillows to the sample cell (the prepared sample). Cap the cell and shake gently for 20 seconds.
Note: Shaking gently dissipates bubbles which may form in samples containing dissolved gases.
- 3. Wait 3 minutes. During this period, proceed with steps 4-8.
Note: A pink color will develop if chlorine is present.
Note: Accuracy is not affected by undissolved powder 66
CHLORINE, TOTAL, High Range, continued
- 4. Fill another 1-cm/10-mL sample cell to the 10-mL line with sample (the blank). Cap.
- 5. Place the blank into the cell holder, with the diamond mark facing you and the tab to the side.
Tightly cover the cell with the instrument cap (flat side should face the back of the instrument).
Note: Wipe liquid off sample cells.
- 6. Press: ZERO The instrument will turn on and the display will show followed by 0.0.
Note: High range displays only to tenths mg/L.
Note: The instrument automatically shuts off after 1 minute. If this occurs, the last zero is stored in memory.
Press READ to complete the analysis.
67
CHLORINE, TOTAL, High Range, continued
-
- 7. Within three minutes after the 3-minute period, place the sample cell from step 2 into the cell holder.
Note: Wipe liquid off sample cells.
- 8. Tightly cover the cell with the instrument cap (flat side should face the back of the instrument).
- 9. Press: READ The instrument will show
--- followed by the results in mg/L chlorine (Cl 2).
Note: If the sample temporarily turns yellow after reagent addition or shows overrange (flashing 5.0), dilute a fresh sample and repeat the test. A slight loss of chlorine may occur. Multiply the result by the dilution factor.
68
CHLORINE, TOTAL, High Range, continued Accuracy Check and Interferences See page 60.
REQUIRED REAGENTS Description Unit Cat. No.
DPD Total Chlorine Reagent Powder Pillows.........................
100/pkg........ 21056-69 or DPD Total Chlorine Reagent AccuVac Ampuls..................... 25/pkg........ 25030-25 REQUIRED APPARATUS Beaker, 50 mL..................................
each......... 500-41 OPTIONAL REAGENTS Chlorine Standard Solution Voluette Ampules, 50-75 mg/L, 10 mL....................
.............. 16/pkg........ 14268-10 DPD Free Chlorine Reagent w/dispensing cap......................
250 tests........ 21056-29 Potassium Iodide Solution, 30 g/L............................... 100 mL MDB*.........
343-32 Sodium Arsenite Solution, 5 g[L..................................
100 mL MDB......... 1047-32 Sodium Hydroxide Standard Solution, I N.................... 100 mL MDB......... 1045-32 Sulfuric Acid Standard Solution, 1 N......................... 100 mL MDB 1270-32 Water, deionized.........................
4 L.
272-56
- Marked Dropper Bottle 69
CHLORINE, TOTAL, High Range, continued OPTIONAL APPARATUS Description UnitCat. No.
AccuVac Snapper Kit.......................
each...
24052-00 Batteries, AAA, alkaline.......................
4/pkg...
46743-00 Caps for 10-mL sample cells.......................
12/pkg...
24018-12 Cylinder, graduated, 25 mL, poly.......................
each.1081-40 Cylinder, graduated, 100 mL, PMP.......................
each.
2172-42 sensiollTMl Basic Portable pH Meter, with electrode.................. each...
51700-10 Pipet, TenSette, 0.1 to 1.0 mL.....................................
each...
19700-01 Pipet Tips, For 19700-01 TenSette.....................................
50/pkg...
21856-96 Sample Cells, 10-mL with screw caps.....................................
6/pkg...
24276-06 REPLACEMENT PARTS Cap for 1-cm/10 mL sample cell.....................................
each...
52626-00 Instrument Cap/light shield............................................................ each......... 46704-00 Instrument Manual.....................................
each...
46760-88 Sample Cells, 1-cm/10-mL.....................................
each...
41658-02 70
USING Spec&m SECONDARY STANDARDS Specv/ Secondary Standards are available to quickly check the repeatability of the Pocket Colorimeterm instrument. After initial readings for the Spec/ standards are collected, the standards can be re-checked as often as desired to ensure the instrument is working consistently.
The standards do not ensure reagent quality nor do they ensure the accuracy of the test results. Analysis of real standard solutions using the kit reagents is required to verify the accuracy of the entire Pocket Colorimeter system. The Specv/ Standards should NEVER be used to calibrate the instrument. The certificate of analysis lists the expected value and tolerance for each Spec-V Standard.
Note: Before proceeding, make sure the instrument is in the low (LO) range mode. See page 37.
Using the Specv Standards
- 1. Place the Specd/ blank into the cell holder with the alignment mark facing the keypad. Tightly cover the cell with the instrument cap.
- 2. Press ZERO. The display will show 0.00.
71
USING SpecVM SECONDARY STANDARDS, continued
- 3. Place the STD 1 cell into the cell holder. Tightly cover the cell with the instrument cap.
- 4. Press READ. Record the concentration reading.
- 5. Repeat steps 3 and 4 with cells labeled STD 2 and STD 3.
- 6. Compare these readings with previous readings to verify the instrument is returning consistent readings. (If these are the first readings, record them for comparison with later readings.)
Note: f the instrument is user-calibrated, initial standard readings of the SpecV Standards will need to be read again when using the user calibration.
72
GENERAL INFORMATION
- a.
I At Hach Company, customer service is an important part of every product we make.
With that In mind, we have compiled the following information for your convenience.
I
' -,&
Li -.
' ;-
-'. 1-1 4" "..'
! "., I '!
.1 I--
73
74
HOW TO ORDER By Telephone:
6:30 a.m. to 5:00 p.m. MST Monday through Friday (800) 227-HACH (800-227-4224)
By FAX:
(970) 669-2932 (Hach Loveland)
By Mail:
Hach Company P.O. Box 389 Loveland, Colorado 80539-0389 U.S.A.
For order information by E-mail:
orders @hach.com Information Required:
Hach account number (if available)
Billing address Shipping address Your name and phone number Purchase order number Catalog number Brief description or model number Quantity Technical and Customer Service (USA only)
Hach Technical and Customer Service Department personnel are eager to answer questions about our products and their use and to take your orders. Specialists in analytical methods, they are happy to put their talents to work for you.
Call 1-800-227-4224 or E-mail techhelp@hach.com.
75
HOW TO ORDER, continued International Customers Hach maintains a worldwide network of dealers and distributors. To locate the representative nearest you, send E-mail to intl@hach. corn or call (970) 669-3050.
In Canada Hach Sales & Service Canada Ltd., Manitoba, Canada Telephone: (204) 632-5589; FAX: (204) 694-5134 76
REPAIR SERVICE Authorization must be obtained from Hach Company before sending any items for repair. Please contact the Hach Service Center serving your location.
In the United States:
Canada:
Hach Company Hach Sales & Service Canada Ltd.
100 Dayton Avenue 1313 Border Street, Unit 34 Ames, Iowa 50010 Winnipeg, Manitoba R3H OX4 (800) 227-4224 (USA only)
(800) 665-7635 (Canada only)
FAX: (515) 232-3835 Telephone: (204) 632-5598 FAX: (204) 694-5134 E-mail: canada@hach.com Latin America, Caribbean, Africa, Europe, the Middle East, Far East, Indian Subcontinent:
or Mediterranean Africa:
Hach Company World Headquarters HACH Company, c/o P.O. Box 389 Dr. Bruno Lange GmbH Loveland, Colorado 80539-0389 U.S.A.
WillstUtterstr. 11 Telephone: (970) 669-3050 D-40549 Dusseldorf, Germany FAX: (970) 669-2932 Telephone: +49/[0]211.52.88.0 E-mail: intl@hach. com.
FAX: +49/[0]211.52.88.231 77
I I
WARRANTY Hach warrants most products against defective materials or workmanship for two years from the date of shipment.
HACH WARRANTS TO THE ORIGINAL BUYER THAT HACH PRODUCTS WILL CONFORM TO ANY EXPRESS WRITTEN WARRANTY GIVEN BY HACH TO THE BUYER. EXCEPT AS EXPRESSLY SET FORTH IN THE PRECEDING SENTENCE, HACH MAKES NO WARRANTY OF ANY KIND WHATSOEVER WITH RESPECT TO ANY PRODUCTS. HACH EXPRESSLY DISCLAIMS ANY WARRANTIES IMPLIED BY LAW, INCLUDING BUT NOT LIMITED TO ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
LIMITATION OF REMEDIES: Hach shall, at its option, replace or repair nonconforming products or refund all amounts paid by the buyer. THIS IS THE EXCLUSIVE REMEDY FOR ANY BREACH OF WARRANTY.
LIMITATION OF DAMAGES: IN NO EVENT SHALL HACH BE LIABLE FOR ANY INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND FOR BREACH OF ANY WARRANTY, NEGLIGENCE, ON THE BASIS OF STRICT LIABILITY, OR OTHERWISE.
This warranty applies only to Hach products purchased and delivered in the United States.
Catalog descriptions, pictures and specifications, although accurate to the best of our knowledge, are not a guarantee or warranty.
For a complete description of Hach Company's warranty policy, request a copy of our Terms and Conditions of Sale for U.S. Sales from our Customer Service Department.
78
79
I HA HACH COMPANY WORLD HEADQUARTERS RO. Box 389 Loveland, Colorado 80539-0389 Telephone: (970) 669-3050 FAX: (970) 669-2932 FOR TECHNICAL ASSISTANCE, PRICE INFORMATION AND ORDERING:
In the U.S.A. - Call toll-free 800-227-4224 Outside the U.S.A. - Contact the HACH office or distributor serving you.
On the Worldwide Web - www.hach.com; E-mail - techhelp@hach.com