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Office of Ground Water and Drinking Water 

January 19, 2010 

MEMORANDUM 

SUBJECT: Basis for Expedited Approval of EPA Method 557 for the Analysis of 

Dalapon 

FROM: Glynda Smith, Chemist 

Technical Support Center 

TO: The Record 

In the previous expedited methods action (Nov. 10, 2009), EPA Method 557, a directinjection method for the analysis of haloacetic acids (HAAs) by use of ion 

chromatography tandem mass spectrometry (IC-MS/MS), was approved for the analysis 

of HAAs and bromate. Dalapon can also be measured concurrently with the haloacetic 

acids using Method 557. This memo documents the comparison of Method 557 to EPA 

methods approved through rulemaking for dalapon. It provides the background 

information on why EPA is approving this method for dalapon using the expedited 

method approval process. 

EPA has established a Maximum Contaminant Level (MCL) of 200 μg/L for dalapon1. 

EPA has approved six methods for the analysis of dalapon through the notice-andcomment rulemaking process2

: EPA Method 552.1, EPA Method 515.1, EPA Method 

552.2, EPA Method 515.3, EPA Method 515.4 and EPA Method 552.3. The benchmark 

for alternative methods was established when the regulations were promulgated. Thus, 

the performance characteristics of EPA Method 557 were compared to the characteristics 

of previously approved methods for dalapon. The performance characteristics presented 

in this memo include detection limit as defined in 40 CFR Part 136 Appendix B, and 

precision and accuracy in drinking water matrices. 

Method 557 achieves several significant goals, which were the primary impetus for 

developing an alternate method. The currently approved methods for compliance 

monitoring of dalapon require extraction into an organic solvent, and then methylation 

using either diazomethane or acidic methanol. Extracts are analyzed by gas 

chromatography (GC) with electron capture detection (ECD). To account for 

methylation inefficiency, each of the approved methods requires the processing of at least 

five calibration standards to prepare an internal-standard-based, procedural calibration 

curve. The direct-injection method (557) simplifies the analysis of dalapon by 

eliminating the extraction and derivatization steps and the associated procedural 

calibration. An additional benefit of the new approach is improved confidence in the 

qualitative identification of detected analyte. The MS/MS detection technique is more 
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selective (much less subject to interfering chemical species in the sample) than the ECD 

detector. 

Table 1 provides a comparison of detection limits for dalapon excerpted from the method 

performance sections of approved EPA Methods 552.2, 552.3, and 515.4 to EPA Method 

557. A comparison of precision and accuracy data for dalapon are presented in Tables 2 

and 3. These data were obtained by fortifying drinking water samples from surface water 

and ground water sources (Table 2) and a high-ionic strength matrix (Table 3) with 

dalapon and performing replicate analyses. Table 3 compares the two methods for which 

such data are available. The information in Table 3 is intended to demonstrate acceptable 

performance in high ionic strength matrices (reagent water fortified with high 

concentrations of common anions) for the analysis of dalapon, because ion 

chromatography is subject to adverse matrix effects under such conditions. 

The detection level for dalapon in Method 557 is similar to those achieved by the 

approved methods. The LCMRL for dalapon easily meets the regulatory MCL 

requirement. The accuracy (as shown by % Recovery) and precision (relative standard 

deviation—RSD) data for Method 557 are similar to the other approved methods. 

The performance characteristics of EPA Method 557 are within the range of those 

observed using the promulgated methods for dalapon. Therefore, EPA Method 557 is 

equally as effective as the promulgated methods for determining the concentration of 

dalapon in drinking water. 

1

Maximum Contaminant Level (MCL). Source: 40 CFR 141.61(c). 

2

Approved methods promulgated in the drinking water regulations at 40 CFR 

141.24(e)(1). 
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a Table 1. Method Detection Limit Comparison for Dalapon in Drinking Water. 

 (All concentrations are in μg/L) 

MDLs published in Approved Methods a DLs / LCMRLse publi

 in EPA 557 f

EPA 552.2 Rev 1.0 b EPA 552.3 Rev. 1.0 c EPA 515.4 Rev 1.0d

0.119 0.024 0.054/0.074 0.038/0.41 

a Method Detection Limit (MDL) calculated according to procedure published at 40 CFR 136 Appendix B. b Data for EPA Method 552.2 are from Table 2 in the method. c Data for EPA Method 552.3 are from Table 5 (methyl-t-butyl ether extraction) in the method. d Data for EPA Method 515.4 are from Table 4 in the method. Values listed are those obtained for the primary c

confirmation column. 

e Detection Limits (DLs) calculated according to procedure published at 40 CFR 136 Appendix B. Data were acq

Lowest Concentration Minimum Reporting Levels (LCMRLs) calculated according to the procedure described in Statistical Procedures for Determination and Verification of Minimum Reporting Levels for Drinking Water MetTechnol. 2006; 40, 281-288. 

f Data for EPA Method 557 are from Tables 5 and 6 in the method. 
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Table 2. Precision and Accuracy Comparison between EPA Methods 552.2, 552.3, 515.4, and 557 for 

Drinking Water. 

Matrixe

EPA 552.2 Rev 1.0a EPA 552.3 Rev 1.0b EPA 515.4 Rev 1.0c 

Concf

(μg/L) 

%Recovery 

(RSD)g

Concf

(μg/L) 

%Recovery 

(RSD)g

Concf

(μg/L) 

%Recovery 

(RSD)g

Co

(μg

SW 2.0 98.0 (8.0) 1.0 107 (2.2) 1.0 104 (2.1) 0.72 

10 99.6 (0.90) 10 100 (2.5) 0.72 

GW 2.0 100 (11) 0.19 + 1.0 112 (1.1) 1.0 105 (1.5) 0.37 

0.19 + 10 97.8 (1.1) 10 97.0 (5.5) 0.37 

a Data for EPA Method 552.2 are from Tables 5 and 7 in the method. b Data for EPA Method 552.3 are from Tables 8, 9, 10, and 11 in the method (methyl-t-butyl ether extraction). c Data for EPA Method 515.4 are from Tables 7, 8, 9, and 10 in the method. d Data for EPA Method 557 are from Tables 9 and 10 in the method. e Matrix: SW = drinking water from a surface water source; GW = drinking water from a ground water source f When two concentrations are listed on one line, the first number is the background concentration and the second 

fortification concentration. A single concentration represents the fortification concentration and indicates there w

background concentration of the analyte. 

g RSD = relative standard deviation of seven or more replicates. 
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Table 3. Precision and Accuracy Comparison between EPA Method 552.2 and EPA Method 557 for D Water—Measured in High Ionic Strength Matrix. 

EPA Method 552.2, Rev 1.0 a EPA Method 557 b

Concentration c (μg/L) % Recovery (RSD) d Fortification μg/L % Recovery (RSD) 

0.675 + 2.0 85.8 (11) 1.0 113 (4.5) 15 93.2 (6.6) 

a Data for EPA Method 552.2 are from Table 6 in the method. Matrix: tap water (groundwater source), hardness 

calcium carbonate (CaCO3). The matrix contained low concentrations of HAAs prior to fortification. 

b Data EPA Method 557 are from Table 8 in the method. Matrix: synthetic sample matrix prepared in reagent waof 100 mg/L ammonium chloride, 20 mg/L nitrate anion, 150 mg/L bicarbonate anion, 250 mg/L chloride anion, anion. The matrix did not contain HAAs before the fortification. c The first number is the background concentration and the second number indicates the fortification concentratiod RSD = relative standard deviation of seven or more replicates.