Hach Method 10260

Determination of Chlorinated Oxidants (Free and Total) in Water Using Disposable Planar
Reagent

- filled Cuvettes and Mesofluidic Channel Colorimetry

Revision 1 .0

April 201 3

1. Scope and Application

1.1 This method covers the determination of chlorinated oxidants in water using DPD
chemistry in a disposable reagent

- filled cuvette with m esofluidic channel colorimetry.

1.2 For this method, chlorinated oxidants are defined as the aqueous species that incl ude free
chlorine (Cl 2 , HOCl, and OCl - ), monochloramine, and total chlorine (monochloramine,
dichloramine, and trichloramine).

1.3 The applicable analytical measurement range of this method is 0. 12 mg/L to 4.6 mg/L as

Cl 2

.

1.4 The performance of this method is equally effective to the US EPA reference methods of

SM 4500

- Cl G, EPA Method 330.5, and Hach Methods 8021 and 8167 and may be used
for USEPA drinking water and wastewater regulatory reporting programs.

2. Summary of Metho d

2.1 This is a colorimetric disposable planar DPD reagent

- filled cuvette version of the EPA

Reference DPD Method 330.5, Standard Method 4500

- Cl G, and Hach Methods 8021
and 8167. A mesofluidic pump system is used to draw a water sample through the

cuvet te, where the sample is mixed with the appropriate reagents, and then move d to the
optical channel where chlorine is measured at a wavelength between 490 to 530 nm

.

3. Definitions

3.1 Calibration Check Standard (CC) : An aqueous calibration standard containing the method analyte that is analyzed periodically to verify the accuracy of the existing calibration.

3.2 Initial demonstration of capability (IDC) : Replicate reference samples are analyzed to demonstrate the ability to obtain acceptable precision and accuracy. An IDC is performed the first time this method is used by each operator.

3.3 Laboratory reagent blank (LRB) : An aliquot of reagent water or other blank matrix that is treated as a sample including exposure to all glassware, equipment, solvents, and reagents that are used with other samples. The LRB is used to determine if method analytes or

1other interferences ar e present in the laboratory environment, the reagents or the

apparatus.

3.4 Linear calibration range (LCR): The concentration range over which the instrument response is linear.

3.5 Material safety data sheet (MSDS) : Written information provided for t he chemical reagents concerning a chemical’s toxicity health hazards, physical properties, fire, and reactivity data including storage, spill and handling precautions.

3.6 Minimum Reporting Level (MRL): The lowest level at which the entire analytical sys tem gives a reproducible signal that meets the method quality objectives. It is never lower than the concentration of the lowest calibration check (CC) standard.

3.7 Quality control sample (QCS): A solution of method analyte of known concentration. The Q CS is obtained from a source external to the laboratory or is prepared from standards obtained from a different source than the calibration standards. The purpose is to check laboratory performance using test materials that have been prepared independently from the normal calibration process.

3.8 Reagent water : Water demonstrated to be free from the method analyte and interfering

substances

4

. Interferences

4 .1 As with all DPD methods for the measurement of chlorine, this method is equally subject

to the same interferences of oxidized forms of iron and manganese.

4 .2 No other interferences have been encountered with chemical species found naturally in drinking water or added as treatment chemicals.

5

. Safety

5 .1 The toxicity or carcinogenicity of e ach reagent used in this method has not been precisely determined; however, each chemical should be treated as a potential health hazard. Exposure to these chemicals should be reduced to the lowest possible level. It is suggested that the laboratory perf orm personal hygiene monitoring of each analyst using this method and that the results of this monitoring be made available to the analyst.

5 .2 This method does not address all safety issues associated with its use. The laboratory is responsible for maintaining a safe work environment and a current awareness file of OSHA regulations regarding the safe handling of any chemicals specified in this method. A reference file of material safety data sheets (MSDSs) should be available to all personnel involv ed in these analyses. Additional information on laboratory safety can be

found in Sections 1 6

. 2 and 1 6

. 3

.

26

. Equipment

6 .1 Sample containers (plastic or glass) free from chlorine oxidants and chlorine demand.

6 .2 Colorimetric Pump/Meter System

– Hach C ompany Mesofluidic Pump/Meter designed for Hach Planar DPD Reagent Filled Cuvettes (PFRC)

6 .3 Disposable DPD Reagent Filled Cuvettes

– Hach Company Chlorine PRFC strips

.

7

. Reagents and Standards

7 .1 Reagent Water

– Purified water (typically either deionized or distilled). Reagent water can be purchased from a scientific supply company, if it is not available on site. If a chlorine demand is present, suggested procedures for preparing chlorine demand

- free

water are included in ASTM D 1253

- 03 and Standard Method 4500

- Cl ).

7 .2 Chlorine Standard Solution

– Hach Company Catalog Number 1426820, 50

– 75 mg/L as

Cl 2 , or equivalent.

8

. Sample Collection, Preservation, and Storage

8 .1 Collect samples in chlorine

- demand free amber glass or plastic containers, filling the

container to headspace free. Avoid agitation during sampling. Analyze within 15 minutes

of sample collection, as chlorine in aqueous solution is not stable.

9

. Quality Control

9 .1 Quality Control (QC) requirements include the Initial Demonstration of Capability and ongoing QC requirements that must be met when preparing and analyzing field samples. This section describes each QC parameter, its required frequency, and the performance

criteria that must be met in order to meet EP A quality objectives. These QC requirements are considered the minimum acceptable QC criteria. Laboratories are encouraged to institute additional QC practices to meet their specific needs.

9 .2 INITIAL DEMONSTRATION OF CAPABILITY (IDC)

– The IDC must be successfully performed prior to analyzing any field samples. Prior to conducting the IDC, the analyst must meet the calibration requirements outlined in Section 10. Requirements for the initial demonstration of laboratory capability are described in the fo llowing sections.

9 .2.1 DEMONSTRATION OF LOW SYSTEM BACKGROUND

– Analyze a LRB after processing through all sample collection steps outlined in Section 8.1

. The
method blank concentration must be ≤ 1⁄3 the MRL.

9.2.2 INITIAL DEMONSTRATION OF ACCURACY

– Pre pare and analyze five independent reference samples at the same concentration. The concentration of the

3samples should be at or below the mid range of the calibration curve. Calculate the average chlorine concentration for the five analyses. The average co ncentration for the five replicates must be within ± 15% of the expected value.

9. 2.3 INITIAL DEMONSTRATION OF PRECISION

– Using the same set of replicate data generated for Section 9.2.2 calculate the standard deviation and relative standard deviation ( R SD ) of the replicate values. The RSD is calculated using the equation %100×= XSRSD where S is the standard deviation for the replicate values, and X is the average value for the replicates. The RSD of the results of the replicate analyses must be ≤15%.

9.3 ONGOING QC REQUIREMENTS

– This section describes the ongoing QC criteria that must be followed when processing and analyzing field samples.

9. 3 .1 DEMONSTRATION OF LOW SYSTEM BACKGROUND

– Analyze a LRB with each analytical batch. The LRB should be processed through all sample collection steps outlined in Section 8.1. The method blank concentration must be
≤ 1⁄3 the MRL.

9.3.2 CONTINUING CALIBRATION C HECK

– Analyze a CCC with each analytical batch. Prepare an aqueous calibration check standard at a concentration near the expected concentration of the water samples. Over time, vary the calibration check standard concentration. The grab sample measured c oncentration of the calibration check standard must be within ± 15% of the expected value. If this criterion is not met, then the analyst must identify and resolve the problem.

9.4 Laboratories/water systems are encouraged to institute additional QC prac tices to meet their specific needs. The remainder of this section describes various optional QC procedures that may be incorporated into a QC program.

9.4.1 QUALITY CONTROL SAMPLE (QCS)

– Analysis of a sample from an external source (different from the c alibration standards) provides an independent check of the calibration of the method. It is recommended semiannually or any time a new calibration curve is validated.

9.4.2 PROFICIENCY TESTING (PT) or PERFORMANCE EVALUATION (PE) SAMPLE

– Successful parti cipation in a PT or PE Study is a good QC tool for demonstrating proficiency with the grab sample method. A

certified solution of chlorine whose concentration is unknown to the analyst can be purchased by the laboratory/water system. An aliquot of the

cert ified solution is added to a known volume of reagent water and analyzed as a grab sample. The analytical results are reported to the PT/PE Study Provider where they are compared to data from all analyses of the sample. Acceptance criteria are established b y the provider for each study.

10. Initial Calibration Check and Calibration Verification

410.1 Initial Calibration Check

10.1.1 Prepare a set of aqueous calibration check standards bracketing the range of the

method . The lowest concentration calibration standard should be 0.20 mg/L Cl 2 2. The highest standard should be 4.0 mg/L Cl 2

.

10. 1. 2 Analyze the calibration standards according to the manufactures instrument
instructions and the procedures in Section 11 of th is method.

10. 1. 3 Compare the results of each measured concentration to that of the expected value.
Each measured calibration verification point must be within ± 15% of its expected value.

10. 1

. 3.1 If the measured value is outside the required ± 15%, prepare a new calibration
verification standard and analyze.

10. 1. 3.2 I f the new calibration verification standard is outside the required ± 15%, the
factory installed calibration must be updated following the manufacturer’s instructions.

Otherwise, send the chlorine meter to the manufacturer for repair or updating.

10.2 Calibration Verification

10.2.1 Prepare an aqueous calibration verification standard at 2.0 mg/L Cl 2

.

10.2.2 Analyze the calibration verification standard according to the manufa ctures instrument instructions and the procedures in Section 11 of this method.

10.2.3 Compare the result of the measured concentration to that of the expected value of
2.0 mg/L Cl 2 . The measured calibration verification point must be within ± 15% of it s expected value.

10.2.3.1 If the measured value is outside the required ± 15%, prepare a new calibration
verification standard and analyze.

10.2.3.2 If the new calibration verification standard is outside the required ± 15% limit,
repeat steps in th e Initial Calibration Check Section 10.1.

511. Procedure

11.1 Press and hold the power button on the meter until the title screen is displayed.

11.2 When the meter passes all internal functional checks on start up, and the user has verified the optical performance the screen prompts the user to insert a PRFC.

11.3 Insert a chlorine

- PRFC strip into the meter slot. Make sure to push the PRFC all the way

into the slo t and there is tactile feedback that the PRFC has interfaced with the pump. The

meter will recognize the barcode on the PRFC and will display the parameter on the display.

11.4 Rinse the sample container 2

- 3 times and then fill the sample container to the line.

11.5 Dip the PRFC into the sample and wait for a beep to acknowledge that the system has pulled the sample into the PRFC . The system uses a conductivity detector to determine when the PRFCs have been dipped into the water. Withdraw the PRFC from the sample and the test will automatically start. Once the test is finished the results will be stored and displayed on the screen. Remove the PRFC out of the instrument and dispose of in accordance with waste management procedures in Section 15 of this method.

12. Data Analysis and Reporting

12.1 The result of the sample measurement is displayed on the meter. No other calculation is required unless the sample was diluted prior to analysis and measurement.

12.2 If the sample was diluted prior to analysis and measurement , multiply the answer by the appropriate dilution factor:

Total Volume
Dilution Factor = _____________ Sample Volume

where: Sample Volume = Aliquot of sample taken for dilution (mL) Total Volume = Volume to which sample volume is diluted (mL) Corrected Concentration = Observed concentration x dilution factor

12.3 Report results in milligrams chlorine per liter (mg/L Cl 2 ).

12.4 Report results to two significant figures from 0.1 2 to 4

. 60 mg/L Cl 2

.

13. Method Performance

13.1 Using the Hach PRFCs, three different laboratories reported that the MDL of replicate

6observations (n =21) of a calibration standard containing ~0.2 mg/ L Cl 2 was 0.019 mg/L

Free Cl 2 and 0.025 mg/L Total Cl 2 respectively.

13.2 With multiple batches of PRFCs, the relative standard deviation of sets of observations (n = 21) of a calibration standard containing ~2.0 mg /L Cl 2 was 2.30% for Free Cl 2 and

2.88% for Total Cl 2

.

14. Pollution Prevention

14.1 Dispose of PRFC strips according to the waste management requirements in Section 15

of this method.

14.2 Standards should be prepared in volumes consistent with laboratory use to minimize the volume of expired standards to be disposed.

15. Waste Management

15. 1 It is the laboratory’s responsibility to comply with all federal, state, and local regulations governing waste management, particularly the hazardous waste identification rules and land disposal restrictions, and to protect the air, water, and land by mi nimizing and controlling all releases from fume hoods and bench operations. Compliance with all sewage discharge permits and regulations is also required.

15.2 Excess reagents, samples and method process wastes should be characterized and disposed of in a n acceptable manner. The MSDS sheet gives details of product composition and may be consulted for guidance on waste disposal.

15.3 For further information on waste management, consult “The Water Management Manual for Laboratory Personnel”, and “Less is Be tter: Laboratory Chemical Management for Waste Reduction”, both available from the American Chemical Society’s Department of Government Relations and Science Policy, 1155 16th Street N.W., Washington DC,

20036.

16. References

16.1 “Carcinogens

- Working Wi th Carcinogens”, Department of Health, Education, and Welfare, Public Health Service, Center for Disease Control, National Institute for Occupational Safety and Health, Publication No. 77

- 206, August 1977.

16.2 “OSHA Safety and Health Standards, General Industry”, (29 CFR 1910), Occupational Safety and Health Administration, OSHA 2206 (Revised, January 1976).

16.3 “Safety in Academic Chemistry Laboratories”, American Chemical Society, Committee

on Chemical Safe ty, 3rd Edition, 1979.

16.4 Standard Test Method f or Residual Chlorine in Water, ASTM D1253

- 08

716.5 Standard Method 4500

- Cl G, Standard Methods for the Examination of water and

Wastewater

17. Acceptance Criteria for Performance Tests

17.1 Acceptance Criterion Section Limit (%)

17.1.1 Quantit at ion Range

Lower range of quantitation

– 1.2 mg/L Cl 2 Upper range of quantitation

– 4.6 mg/L Cl 2

17.1.2 Initial accuracy and precision

Accuracy= ±15%

Precision=15%

17.1.3 Continuing calibration Check Accuracy=±15%

17.1.4 Calibration verification

Accuracy=±15%

8