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Office of Ground Water and Drinking Water

February 29, 2016

MEMORANDUM

SUBJECT: Basis for Expedited Approval of Methods from Hach Company

FROM: William Adams, Chemist, and Glynda A. Smith, Chemist,

OGWDW/SRMD/TSC

TO: The Record

This memo documents the reviews that were conducted on methods submitted for evaluation 

through the drinking water Alternate Test Procedure (ATP) program by Hach Company. The memo 

provides the background information on why EPA is approving these methods through the expedited 

methods approval process. Each method is discussed individually below in the order in which they 

appear in the Federal Register notice:

Hach Method 10241: Spectrophotometric Measurement of Free Chlorine in Drinking Water

Hach Method 10241 was submitted as an alternate test procedure to Standard Method 4500-Cl G, 

which is approved in the drinking water regulations at 40 CFR 141.74(a)(2) and 40 CFR 141.131(c)(1) 

for the determination of free chlorine in drinking water.

In Hach Method 10241, free chlorine is converted to monochloramine by addition of an ammonia 

solution to a drinking water sample. In the presence of a cyanoferrate catalyst, monochloramine 

reacts with a substituted phenol to form an intermediate monoamine compound. The intermediate 

monoamine compound couples with excess substituted phenol to form a green indophenol 

compound which is measured spectrophotometrically at 655 nm. The approved Standard Method 

4500-Cl G uses a DPD indicator for spectrophotometric determination of residual free chlorine in 

drinking water samples. DPD is subject to interferences associated with the presence of manganese, 

chloramines, and other oxidants. Hach Method 10241 is not subject to such interferences.

A multi-laboratory validation study was conducted to compare the performance of Hach Method 

10241 with Standard Method 4500-Cl G. The data from three laboratories were used in the multilaboratory validation study. An initial demonstration of capability was performed using different

drinking water matrices (e.g. low ionic strength water, “hard” water with 250 mg/L CO3, and high TOC 

water) at free chlorine concentrations ranging from 0.05 to 4.0 mg/L. Precision and recovery data and 

detection limits were also determined using low and high ionic strength water and tap water samples

drawn from both ground and surface source waters. The complete data summary is provided in the

Hach ATP Validation Report. Briefly, the results are as follows:

 Detection limits determined as MDLs for the three laboratories ranged from 0.02 mg/L to 

0.09 mg/L for Hach Method 10241 and 0.02 mg/L to 0.03 mg/L for the reference Standard 

Method 4500-Cl G in low ionic strength water. MDLs ranged from 0.03 mg/L to 0.05 mg/L 

for Hach Method 10241 and 0.02 mg/L to 0.03 mg/L for the reference Standard Method 

4500-Cl G in high ionic strength water. The pooled MDL results for Hach Method 10241
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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 pooled MDL results for Standard Method 4500-Cl G

were determined to be 0.02 mg/L for low ionic strength matrix water and 0.02 mg/L for 

high ionic strength matrix water.

 

 The average recovery for IPR samples in low ionic strength water for the three 

laboratories ranged from 94% to 97% for Hach Method 10241 and 94% to 98% for the 

reference Standard Method 4500-Cl G. The average recovery for IPR samples in high ionic 

strength water for the three laboratories ranged from 93% to 97% for Hach Method 

10241 and 95% to 99% for Standard Method 4500-Cl G. The pooled low ionic strength 

matrix recovery results ranged from 89.5% to 101% with a 95% precision of 0.02 for Hach

Method 10241 and 89.4% to 104% with a 95% precision of 0.02 for Standard Method 

4500-Cl G. The pooled high ionic strength matrix recovery results ranged from 84.8% to 

104% with a 95% precision of 0.02 for Hach Method 10241 and 88.3% to 105% with a 

95% precision of 0.04 for Standard Method 4500-Cl G.

 The average matrix spike recovery results for the three laboratories ranged from 96.3% 

to 103% with an RPD range of 0.5 to 2.0 for Hach Method 10241 and 82.5% to 95% with 

an RPD range of 0.8 to 1.3 for the reference Standard Method 4500-Cl G. The pooled 

matrix recovery results ranged from 89.9% to 110% for Hach Method 10241 and 66.8% to 

114% for Standard Method 4500-Cl G.

Based on the results of the validation study, Hach Method 10241 was determined to be equally as 

effective as the reference Standard Method 4500-Cl G in determining free chlorine in finished drinking 

water.

Hach Method 8026: Spectrophotometric Measurement of Copper in Finished Drinking Water

Hach Method 8026 was submitted as an alternate test procedure to EPA method 200.7 for 

determination of copper in drinking water. Method 200.7 is approved in the national primary 

drinking water regulations at 40 CFR 141.23(k)(1) for the determination of copper by inductively 

coupled plasma.

Hach Method 8026 measures cuprous copper colorimetrically after complexation with bicinchoninic 

acid. Measurements are taken using a spectrophotometer set at 560 nm. The intensity of color is 

directly proportional to the copper concentration. Cupric copper in samples is chemically reduced to 

cuprous copper prior to complexation. Interferences are mitigated through the use of a chelating 

agent. This method is performed through the addition of powder pillows containing the required 

reagents to the drinking water samples. EPA Method 200.7 and other approved methods require 

expensive atomic spectroscopy-based instrumentation and skilled analysts. Hach Method 8026 is 

based on well-known complexation principles and uses a less expensive spectrophotometer and prepackaged reagents to determine copper concentrations simply and quickly.

A multi-laboratory validation study was conducted to compare the performance of Hach Method 

8026 with the approved EPA Method 200.7. The data from three laboratories were used in the 

multi-laboratory validation study. An initial demonstration of capability was performed using 

different matrixes (e.g. low ionic strength water, “hard” water with 250 mg/L CO3, and high TOC 

water) at various copper concentrations. Precision and recovery data and detection limits were also 

determined using low and high ionic strength water and tap water matrixes from both ground and 
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surface source waters. The complete data summary is provided in the Hach ATP Validation Report. 

Briefly, the results are as follows:

 Detection limits calculated as MDLs for the three laboratories ranged from 0.02 mg/L to 

0.07 mg/L for Hach Method 8026 and 0.004 mg/L to 0.01 mg/L for the reference EPA 

Method 200.7 in low ionic strength water. MDLs were 0.02 mg/L to 0.05 mg/L for Hach 

Method 8026 and 0.006 mg/L to 0.009 mg/L for the reference EPA Method 200.7 in high 

ionic strength water. The pooled MDL results for the Hach Method 8026 were determined 

to be 0.03 mg/L for low ionic strength matrix water and 0.03 mg/L for high ionic strength 

matrix water. The pooled MDL results for EPA Method 200.7 were determined to be 0.005

mg/L for low ionic strength matrix water and 0.006 mg/L for high ionic strength matrix 

water. 

 The average recovery for IPR samples in low ionic strength water for the three 

laboratories was 97.3% to 106% for Hach Method 8026 and 95.0% to 104% for the 

reference EPA Method 200.7. The average recovery for IPR samples in high ionic strength 

water for the three laboratories was 93.8% to 105% for Hach Method 8026 and 88.4% to 

101% for the reference EPA Method 200.7. The pooled low ionic strength matrix recovery 

results ranged from 84.9% to 117% with a 95% precision of 0.02 for Hach Method 8026

and 82.7% to 118% with a 95% precision of 0.01 for the reference EPA Method 200.7. The 

pooled high ionic strength matrix recovery results ranged from 76.4% to 121% with a 95% 

precision of 0.01 for Hach Method 8026 and 71.0% to 113% with a 95% precision of 0.02 

for the reference EPA Method 200.7.

 The average matrix spike recovery results for the three laboratories ranged from 91.3% 

to 100% with an RPD of 0.0 to 6.1 for Hach Method 8026 and 88.5% to 99.3% with an 

RPD of 0.0 to 1.0 for the reference EPA Method 200.7. The pooled matrix recovery results 

ranged from 79.5 to 110% for Hach Method 8026 and 77.6% to 113% for the reference 

EPA Method 200.7.

Based on the results of the validation study, Hach Method 8026 was determined to be equally as 

effective as the reference EPA Method 200.7 for the determination of copper in finished drinking 

water.

Hach Method 10261: Total Organic Carbon in Finished Drinking Water by Catalyzed Ozone Hydroxyl 

Radical Oxidation Infrared Analysis

Hach Method 10261 was submitted as an alternate test procedure to Standard Method (SM) 5310 C 

for the analysis of total organic carbon (TOC) in drinking water. SM 5310 C is approved in the national 

primary drinking water regulations at 40 CFR 141.131(d)(3) for the determination of TOC using UVpersulfate oxidation.

Hach Method 10261 determines TOC in drinking water using two reaction mechanisms. Ozone and a 

base are added to water to produce hydroxyl radicals. The hydroxyl radicals oxidize organic carbon 

to produce carbon dioxide and sodium oxalate. The sodium oxalate is further oxidized to carbon 

dioxide via acidification in the presence of a manganese catalyst. The carbon dioxide produced by 

both oxidation processes is then measured using non-dispersive infrared spectroscopy. SM 5310 C 

involves a multi-step analysis that can be laborious and may not completely oxidize certain organic 

compounds, leading to low-biased results. Hach Method 10261 uses an advanced oxidation process 

to ensure a more complete oxidation.
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A multi-laboratory validation study was conducted to compare the performance of Hach Method 

10261 with the approved SM 5310 C. The data from three laboratories were used in the multilaboratory validation study. An initial demonstration of capability was performed using different 

matrixes (e.g. low ionic strength water and “hard” water with 250 mg/L CO3) at various TOC 

concentrations. Precision and recovery data and detection limits were also collected using low and 

high ionic strength water and tap water matrixes from both ground and surface source waters. The

complete data summary is provided in the Hach ATP Validation Report. Briefly, the results are as 

follows:

 Detection limits calculated as MDLs for the three laboratories ranged from 0.04 mg/L to 

0.16 mg/L for Hach Method 10261 and 0.004 mg/L to 0.01 mg/L for the reference SM 5310 

C in low ionic strength water. MDLs were 0.06 mg/L to 0.14 mg/L for Hach Method 10261 

and 0.06 mg/L to 0.17 mg/L for the reference SM 5310 C in high ionic strength water. The 

pooled MDL results for Hach Method 10261 were determined to be 0.02 mg/L for low ionic 

strength matrix water and 0.09 mg/L for high ionic strength matrix water. The pooled MDL 

results for SM 5310 C were determined to be 0.10 mg/L for low ionic strength matrix water 

and 0.09 mg/L for high ionic strength matrix water. 

 The average recovery for IPR samples in low ionic strength water for the three 

laboratories was from 99.8% to 100% for Hach Method 10261 and 100% to 102% for the 

reference SM 5310 C. The average recovery for IPR samples in high ionic strength water 

for the three laboratories was 100% for Hach Method 10261 and 100% to 105% for the 

reference SM 5310 C. The pooled low ionic strength matrix recovery results were 100% 

with a 95% precision of 0.01 for Hach Method 10261 and 101% with a 95% precision of 

0.01 for the reference SM 5310 C. The pooled high ionic strength matrix recovery results 

were 100% with a 95% precision of 0.02 for Hach Method 10261 and 102% with a 95% 

precision of 0.06 for the reference SM 5310 C.

 The average matrix spike recovery results for the three laboratories ranged from 101% to 

104% with an RPD of 0.1 to 0.8 for Hach Method 10261 and 102% to 110% with an RPD of 

0.3 to 9.3 for the reference SM 5310 C. The pooled matrix recovery results were 102% for 

Hach Method 10261 and 105% for the reference SM 5310 C.

Based on the results of the validation study, Hach Method 10261 was determined to be equally as 

effective as the reference SM 5310 C for the determination of TOC in drinking water.

Hach Method 10267: Spectrophotometric Measurement of Total Organic Carbon (TOC) in Finished 

Drinking Water

Hach Method 10267 was submitted as an alternate test procedure to Standard Method (SM) 5310 C 

for the analysis of total organic carbon (TOC) in drinking water. SM 5310 C is approved in the national 

primary drinking water regulations at 40 CFR 141.131(d)(3) for the determination of TOC using UVpersulfate oxidation.

Hach Method 10267 determines TOC in drinking water by oxidizing samples using acid persulfate 

digestions to convert TOC into carbon dioxide. The generated carbon dioxide is passed through a 

gas-permeable membrane into an indicator solution that is measured spectrophotometrically at 435 

nm. Interfering inorganic carbon is removed from the sample prior to digestion by acidification and 

agitation. Hach Method 10267 uses simple spectrophotometry and pre-packaged reagents to 
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quickly analyze for TOC concentration.

A multi-laboratory validation study was conducted to compare the performance of Hach Method 

10267 with SM 5310 C. The data from three laboratories were used in the multi-laboratory 

validation study. An initial demonstration of capability was performed using different matrixes (e.g. 

low ionic strength water and “hard” water with 250 mg/L CO3) at various TOC concentrations. 

Precision and recovery data and detection limits were also collected using low and high ionic strength 

water and tap water matrixes from both ground and surface source waters. The complete data

summary is provided in the Hach ATP Validation Report. Briefly, the results are as follows:

 Detection limits calculated as MDLs for the three laboratories ranged from 0.11 mg/L to 

0.65 mg/L for Hach Method 10267 and 0.04 mg/L to 0.17 mg/L for the reference SM 5310 

C in low ionic strength water. MDLs were 0.23 mg/L to 0.39 mg/L for Hach Method 10267 

and 0.07 mg/L to 0.24 mg/L for the reference SM 5310 C in high ionic strength water. The 

pooled MDL results for Hach Method 10267 were determined to be 0.33 mg/L for low ionic 

strength matrix water and 0.25 mg/L for high ionic strength matrix water. The pooled MDL 

results for SM 5310 C were determined to be 0.09 mg/L for low ionic strength matrix water 

and 0.12 mg/L for high ionic strength matrix water.

 

 The average recovery for IPR samples in low ionic strength water for the three 

laboratories was from 102% to 105% for Hach Method 10267 and 101% to 103% for the 

reference SM 5310 C. The average recovery for IPR samples in high ionic strength water 

for the three laboratories was 104% to 107% for Hach Method 10267 and 101% to 107% 

for the reference SM 5310 C. The pooled low ionic strength matrix recovery results were 

97.5% to 109% with a 95% precision of 0.03 for Hach Method 10267 and 98.3% to 104% 

with a 95% precision of 0.01 for the reference SM 5310 C. The pooled high ionic strength 

matrix recovery results were 99.4% to 111% with a 95% precision of 0.02 for Hach 

Method 10267 and 94.1% to 113% with a 95% precision of 0.06 for the reference SM 

5310 C.

 The average matrix spike recovery results for the three laboratories ranged from 97.9% 

to 101% with an RPD of 0.3 to 3.3 for Hach Method 10267 and 99.4% to 104% with an 

RPD of 0.0 to 3.8 for the reference SM 5310 C. The pooled matrix recovery results were 

94.3% to 105% for Hach Method 10267 and 94.4% to 108% for the reference SM 5310 C.

Based on the results of the validation study, Hach Method 10267 was determined to be equally as 

effective as the reference SM 5310 C for the determination of TOC in drinking water.

Hach Method 10272: Spectrophotometric Measurement of Copper in Finished Drinking Water 

(Chemkey)

Hach Method 10272 was submitted as an alternate test procedure to EPA method 200.7 for 

determination of copper in drinking water. Method 200.7 is approved in the national primary 

drinking water regulations at 40 CFR 141.23(k)(1) for the determination of copper by inductively 

coupled plasma.

Hach Method 10272 measures cuprous copper colorimetrically after complexation with bicinchoninic 

acid. Measurements are taken using a spectrophotometer set at 560 nm. The intensity of color is 

directly proportional to the copper concentration. Cupric copper in samples is chemically reduced to 

cuprous copper prior to complexation. Interferences are mitigated through the use of a chelating 
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agent. This method is performed through the use of a copper Chemkey and portable analyzer. 

Chemkeys are a patented Hach technology in which all reagents needed for analysis are contained 

within a single package that, when used with the portable analyzer, allows for the detection of target 

analytes. EPA Method 200.7 and other approved methods require expensive atomic spectroscopybased instrumentation and skilled analysts. Hach Method 10272 is based on well-known 

complexation principles and uses a less expensive spectrophotometer and pre-packaged reagents to 

determine copper concentrations simply and quickly. The analyzer used for Hach Method 10272 adds 

the additional benefit of being a portable analyzer.

A multi-laboratory validation study was conducted to compare the performance of Hach Method 

10272 with EPA Method 200.7. The data from three laboratories were used in the multi-laboratory 

validation study. An initial demonstration of capability was performed using different matrixes (e.g. 

low ionic strength water, “hard” water with 250 mg/L CO3, and high TOC water) at various copper 

concentrations. Precision and recovery data and detection limits were also collected using low and 

high ionic strength water and tap water matrixes from both ground and surface source waters. The

complete data summary is provided in the Hach ATP Validation Report. Briefly, the results are as 

follows:

 Detection limits calculated as MDLs for the three laboratories ranged from 0.01 mg/L to 

0.04 mg/L for Hach Method 10272 and 0.004 mg/L to 0.01 mg/L for the reference EPA 

Method 200.7 in low ionic strength water. MDLs were 0.02 mg/L to 0.03 mg/L for Hach 

Method 10272 and 0.006 mg/L to 0.009 mg/L for the reference EPA Method 200.7 in high 

ionic strength water. The pooled MDL results for the Hach Method 10272 were determined 

to be 0.02 mg/L for low ionic strength matrix water and 0.02 mg/L for high ionic strength 

matrix water. The pooled MDL results for EPA Method 200.7 were determined to be 0.005

mg/L for low ionic strength matrix water and 0.006 mg/L for high ionic strength matrix 

water.

 

 The average recovery for IPR samples in low ionic strength water for the three 

laboratories was 95.8% to 101% for Hach Method 10272 and 95.0% to 104% for the 

reference EPA Method 200.7. The average recovery for IPR samples in high ionic strength 

water for the three laboratories was 90.5% to 97.1% for Hach Method 10272 and 88.4% 

to 101% for the reference EPA Method 200.7. The pooled low ionic strength matrix 

recovery results ranged from 88.4% to 110% with a 95% precision of 0.06 for Hach 

Method 10272 and 82.7% to 118% with a 95% precision of 0.01 for the reference EPA 

Method 200.7. The pooled high ionic strength matrix recovery results ranged from 81.7% 

to 107% with a 95% precision of 0.11 for Hach Method 10272 and 71.0% to 113% with a 

95% precision of 0.02 for the reference EPA Method 200.7.

 The average matrix spike recovery results for the three laboratories ranged from 85.0% 

to 93.5% with an RPD of 0.0 to 4.5 for Hach Method 10272 and 88.5% to 99.3% with an 

RPD of 0.0 to 1.0 for the reference EPA Method 200.7. The pooled matrix recovery results 

ranged from 74.9 to 102% for Hach Method 10272 and 77.6% to 113% for the reference 

EPA Method 200.7.

Based on the results of the validation study, Hach Method 10272 was determined to be equally as 

effective as the reference EPA Method 200.7 for the determination of copper in finished drinking 

water.
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Hach Method 10258 – Determination of Turbidity by 360o Nephelometry

Hach Method 10258 was submitted as an alternate test procedure to Hach FilterTrak Method 10133 

which is approved in the drinking water regulations at 40 CFR 141.74(a)(1) for determination of 

turbidity in drinking water.

In Hach Method 10258, turbidity is determined using a 360 degree nephelometer. A non-incandescent 

light source operates at a wavelength of 660 + 30 nm and light scattered by the sample is collected and 

detected at an angle 90 degrees to the incident light, 360 degrees around the sample vial. This design 

offers improved sensitivity and resolution relative to the approved method.

A multi-facility validation study was conducted to compare the performance of Hach Method 10258 

with the approved Hach method 10133. The study was conducted at seven different drinking water 

facilities - three of them in the European Union (EU) and four in the United States (US). The laboratories 

at the US facilities were all certified to analyze compliance drinking water samples. Of the total seven 

facilities, three facilities produced treated water from both conventional and membrane filtration 

water, two facilities produced only conventional filtration treated water, and two facilities produced 

only membrane filtration treated water. The validation included a total of 120 calibration verification 

tests with Hach Method 10258 and 40 calibration verification tests with the approved Hach Method 

10133, and 300 matrix spike tests ranging over three different turbidity levels, for each of the two 

methods. Because of the large quantity of data evaluated, the following results summarize the key 

data: 

 The rounded minimum quantitation limit for Hach Method 10258 derived from an earlier proof 

of concept study was determined to be 0.0005 Nephelometric Turbidity Units (NTU). 

 The linear range of the Hach Method 10258 is determined to be 0.0005 NTU to 40 NTU, with a 

coefficient of variation of 0.99999 (R2). The range in linearity equates to 4 orders of magnitude, 

1 order of magnitude greater in range and 40 times greater in upper quantitation than the 

approved Hach Method 10133.

 The lowest resolution of the method (lowest level of change in turbidity that can be quantified) 

is less than 0.0001 NTU. The value has a resolution that is at least three times lower than that 

attainable with the approved Hach Method 10133.

 The stability of the Hach Method 10258 360oinstrument as evaluated by the calibration 

verification results over two months of measurements in 10 different drinking waters, with a 

calibration verification range of 1 to 20 NTU, has a range of 1.7% to 3.5%. Hach Method 10133

for the same testing period and drinking water but at a single nominal calibration verification 

turbidity of 1 NTU (0.800 NTU actual), is 4.4%.

 The combined matrix spike recovery for a filtration treated water and facilities, is 101% of 

theoretical with an 8.0% relative standard deviation for Hach Method 10258. Hach Method 

10133 has an equivalent matrix spike recovery of 101% with a relative standard deviation of 

9.2%.

Based on the results of the validation study, Hach Method 10258 was determined to be equally as 

effective as the approved Hach FilterTrak Method 10133 for the determination of drinking water 

turbidity.