## USEPA Validation Study Report for Hach Method 10241 Free Chlorine

Spectro photo metric Measurement of Free Chlorine in Drinking Water

Submitted by:

Hach Company

5600 Lindbergh Drive

Loveland Colorado 8053 8

Cary Jackson

and

Luke Johnson

November 201 5Hach Company Validation Study Report

Measurement of Free Chlorine in Water

, Method 10241

2 Background

Purpose of Study

The purpose of this study is to validate Hach Method 10241, Measurement of Free Chlorine

( Cl 2 ) in Drinking Water for approval and use in USEPA regulatory water compliance and

reporting programs.

Method Summary

An ammonia solution at a pH of 8.3 is added to a sample that contains free chlorine. The free

chlorine rapidly reacts with ammonia to form monochloramine (NH 2 Cl). In the presence of a

cyanoferrate catalyst, the monochloramine reacts with a substituted phenol to form an

intermediate monoimine compound. The intermediate couples with excess substituted phenol

to form a green indophenol compound, which is proportional to the amount of free chlorine in

the sample. A sample blank that contains Monochlor F Reagent corrects for background color

from the reagent and sample. The measurement wavelength is 655 nm for spectrophotometers

or 610 nm for colorimeters.

Method Justification

EPA reference method SM 4500

- Cl G cannot be used to measure free chlorine in the presence

of chloramines, manganese and other oxidants. Proposed Hach Method 10241 for the

Spectrometric Measurement of Free Chlorine overcomes these inte rferences

.

Scope of Method

Hach Method 10241 is applicable for use in drinking water.

Study Design and Objectives

The design and objectives of this validation study are detailed in the Validation Study Plan 1

appended to this report.

Study Implementation

Study Sponsor

The organizational sponsor responsible for managing this study is Hach Company.

1 Hach Validation Study Plan, March 201 5Hach Company Validation Study Report

Measurement of Free Chlorine in Water

, Method 10241

3 Study Participants

The participants, laboratories, and test matrices were selected from geographically diverse

regions of the United States a nd are listed in the following table.

Treated Drinking

Water Matrix

Facility Laboratory Source of Treated

Test Water

Loveland, Colorado Hach Company Surface Water

Cedar Falls , Iowa Test America

- Cedar Falls Surface Water

Brighton , Colorado TRE Environmental Strategies Ground Water

Sample Collection and Distribution

Samples from Cedar Falls, IA and Loveland, CO were taken directly from the laboratory drinking

water tap and analyzed immediately per SM4500

- Cl sampling and storage protocols. The

sample from Brighton, CO was taken from the drinking water plant effluent and delivered to

the TRE laboratory for immediate analysis.

Analysis Description

The description of the type and number of analyses are described in the Validation Study Plan

appe nded to this report.

Data Reporting and Validation

Data Collection, Laboratory Submission, and Validation

For each laboratory performing analyses, results from each test measurement were read from a

DR 1 900 or DR6000 spectrophotometer with built

- in calibration, and manually transferred to an

electronic spread sheet. Each laboratory then submitted the electronic spread sheet to the

Hach Study Director for review and statistical evaluation.

Results

Summary results of the validation s tudy are listed in Tables 1

- 5

. Initial demonstration of

capability is demonstrated by accuracy (bias) and precision data which are generated

throughout the calibration range and at the minimum residual disinfection concentration in

several matrices. Thes e data were collected at the Hach laboratory and are included in Table 1

. The quantitation range and method reporting limits for this method are 0. 1

– 4.5 mg/L Cl 2

.Hach Company Validation Study Report

Measurement of Free Chlorine in Water

, Method 10241

4 Table 1

– Initial Demonstration of Capability for Hach Method 10241

Parameter Concentration

(mg/L)

Average Percent Recovery by Matrix

LIS 250 mg/L CO 3 250 mg/L

CaCO 3 2.5 mg/L TOC

Method Blank 0 0.008 0.007 0.009 0.013

Average Percent Bias by Matrix

LIS 250 mg/L CO 3 250 mg/L

CaCO 3 2.5 mg/L TOC

Accuracy

(bias) 0.05 13.3 20.0 20.0 6.7

0.2 10.0 11.7 0.0 5.0

2.0 4.7 1.3 5.2 6.5

4.0 6.2 1.8 3.2 4.3

Percent Relative Standard Deviation by Matrix

LIS 250 mg/L CO 3 250 mg/L

CaCO 3 2.5 mg/L TOC

Precision 0.05 13.3 0.0 0.0 10.8

0.2 5.6 2.6 8.7 0.0

2.0 0.3 0.3 0.6 1.4

4.0 0.4 0.4 2.7 1.1

Average Percent Bias by Matrix

Loveland DW Brighton DW Keokuk DW

Matrix Spike

Accuracy

(bias) Low 18.3 7.2 6.2

Mid 3.9 5.2 2.4

High 6.5 0.1 8.0

Percent Relative Standard Deviation by Matrix

Loveland DW Brighton DW Keokuk DW

Matrix Spike

Precision Low 1.8 3.0 1.7

Mid 1.8 1.4 0.6

High 3.0 0.8 0.9Hach Company Validation Study Report

Measurement of Free Chlorine in Water

, Method 10241

5 Table 2

– Loveland Colorado Tap Water Performance ResultsHach Company Validation Study Report

Measurement of Free Chlorine in Water

, Method 10241

6 Table 3

– Cedar Falls Tap Water Summary ResultsHach Company Validation Study Report

Measurement of Free Chlorine in Water

, Method 10241

7 Table 4

– Brighton Colorado Drinking Water Plant Summary Results

Development of QC Acceptance Criteria

Q uality control acceptance criteria for method detection limit (MDL)

, initial precision and

recovery (IPR) , and matrix spike recovery are described in Table 5

. Calibration verification is

demonstrated through the accuracy (bias) data. These criteria are based on intra

- laboratory

data.Hach Company Validation Study Report

Measurement of Free Chlorine in Water

, Method 10241

8 Table 5

– Quality Control Performance Criteria for Hach Method 10241

Data Analysis/Discussion

MDL Results

The low ionic strength MDL results for each of the three facilit ies ranged from 0. 02 mg/L to 0.03

mg/L for EPA Reference Method SM 4500

- Cl G and 0. 02 mg/L to 0. 09 mg/L for Hach Method

10241 . The high ionic strength matrix MDL results ranged from 0. 02 mg/L to 0. 03 mg/L for EPA

Reference Method SM 4500

- Cl G and 0. 03 mg/L to 0. 05 mg/L for Hach Method 10241 . The

pooled MDL results for EPA Reference Method SM 4500

- Cl G w ere determined to be 0. 02 mg/L

for low ionic strength m at rix water and 0. 02 mg/L for high ionic strength matrix water. The

pooled MDL results for Hach Method 10241 were determined to be 0. 05 mg/L for low ionic

strength matrix water and 0. 03 mg/L for high ionic strength matrix water. The regulatory limit

establ ished by USEPA for this validation study is 0.2 mg/L as this is the minimum residual

disinfectant concentration in water entering the distribution system as defined in the drinking

water regulations at 40 CFR 141.72(a)(3)

.Hach Company Validation Study Report

Measurement of Free Chlorine in Water

, Method 10241

9 Initial Precision and Recovery Results

The IPR average recovery results for low ionic strength matrix water for each of the three

facilities ranged from 94% to 98 % for EPA Reference Method SM 4500

- Cl G and 94 % to

97% mg/L for Hach Method 10241

. The IPR average recovery results for high ionic strength

matrix water ranged from 95 % to 99 % for EPA Reference Method SM 4500

- Cl G , and 93 % to

97 % for Hach Method 10241 . The pooled low ionic strength matrix recovery results for EPA

Reference Method SM 4500

- Cl G ranged from 89.4 % to 104 % with a 95% precision of 0.0 2 and

89 .5% to 10 1 % with a 95% precision of 0.0 2 for Hach Method 10241 . The pooled high ionic

strength matrix recovery results for EPA Reference Method SM 4500

- Cl G ranged from 88.3 % to

105 % with a 95% precision of 0.0 4 and 84.8 % to 1 04 % with a 95% precision of 0.0 2 for Hach

M ethod 10241

.

Matrix Spike Results

The average matrix spike recovery results of the three facilities ranged from 82.0 % to 97.5 % for

EPA Reference Method SM 4500

- Cl G and 9 6.3 % to 10 3 % for Hach M ethod 10241 . The relative

percent difference for matrix spike recoveries ranged from 0.8 % to 1.3 % for EPA reference

method SM 4500

- Cl G and 0. 5 % to 2 .0% for Hach method 10241

. The pooled matrix spike

results of recovery ranged from 66.8 % to 1 14 % for EPA Reference Method SM 4500

- Cl G and

89.9 % to 110 % for Hach Method 10241

. The 95% Precision of Recovery resul ts for the EPA

Reference Method 4500

- Cl G and Hach Method 10241 were determined to be 0.0 5 and 0.06

respectively.

Conclusion

A validation study was conducted to compare the performance of Hach Method 10241 for the

measurement of Cl 2 in water to that of the EPA Reference Method SM 4500

- G

. The results of

the study indicate that Hach M ethod 10241 is equally effective to that of th e EPA Reference

Method SM 4500

- Cl G for Safe Drinking Water Act monitoring and compliance reporting

programs.