# Page 1 of 5 Office of Ground Water a nd 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 act ion (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-M S/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 docum ents 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 dalapon 1



# . EPA has approved six methods for the an alysis of dalapon through the notice-andcomment rulemaking process 2 

# : EPA Method 552.1, EPA Method 515.1, EPA Method

552.2, EPA Method 515.3, EPA Method 515.4 a nd 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 si gnificant goals, which were the primary impetus for

developing an alternate me thod. The currently approved methods for compliance

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

using either diazomethane or acidic me thanol. Extracts are analyzed by gas

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

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

five calibration standards to prepare an in ternal-standard-based, procedural calibration

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

eliminating the extraction and derivatizati on steps and the associated procedural

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

qualitative identification of detected analyt e. The MS/MS detection technique is more

# Page 2 of 5 selective (much less subject to interfering ch emical species in the sample) than the ECD

detector.

Table 1 provides a comparison of detecti on 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 fortifyi ng drinking water samples from surface water

and ground water sources (Table 2) and a hi gh-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 ma trix effects under such conditions.

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

approved methods. The LCMRL for dala pon 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 Me thod 557 are within the range of those

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

equally as effective as the promulgated me thods 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).Page 3 of 5aTable 1. Method Detection Limit Comparisonfor Dalapon in Drinking Water.(All concentrations are in μg/L)MDLs published in Approved MethodsaDLs / LCMRLsepublishedin EPA 557fEPA 552.2 Rev 1.0bEPA 552.3 Rev. 1.0cEPA 515.4 Rev 1.0d0.119 0.024 0.054/0.074 0.038/0.41aMethod Detection Limit (MDL) calculated accordingto procedure published at 40 CFR 136 Appendix B.bData for EPA Method 552.2 are from Table 2 in the method.cData for EPA Method 552.3 are from Table 5 (methyl-t-butyl ether extraction) in the method.dData for EPA Method 515.4 are from Table 4 in the method. Values listed are those obtained for the primary column/secondaryconfirmation column.eDetection Limits (DLs) calculated according toprocedure published at 40 CFR 136 AppendixB. Data were acquired over 3 days.Lowest Concentration Minimum Reporting Levels(LCMRLs) calculated according to the procedure described in Winslow, S. D. et.al.Statistical Procedures for Determination and Verification of Minimum Reporting Levels for Drinking Water Methods.Environ. Sci.Technol.2006; 40, 281-288.fData for EPA Method 557 are from Tables 5 and 6 in the method.Page 4 of 5Table 2. Precision and Accuracy Comparison between EPA Methods 552.2, 552.3, 515.4, and 557 for Dalapon inDrinking Water.MatrixeEPA 552.2 Rev 1.0aEPA 552.3 Rev 1.0bEPA 515.4 Rev 1.0cEPA 557dConcf(μg/L)%Recovery(RSD)gConcf(μg/L)%Recovery(RSD)gConcf(μg/L)%Recovery(RSD)gConcf(μg/L)%Recovery(RSD)gSW 2.0 98.0 (8.0) 1.0 107 (2.2) 1.0 104 (2.1)0.72 + 2.5 97.8 (3.8)10 99.6 (0.90) 10 100 (2.5)0.72 + 8.0 96.3 (4.8)GW 2.0 100 (11) 0.19 + 1.0 112 (1.1) 1.0 105 (1.5)0.37 + 2.5 95.5 (3.1)0.19 + 10 97.8 (1.1) 10 97.0 (5.5)0.37 + 10 98.5 (3.0)aData for EPA Method 552.2 are fromTables 5 and 7 in the method.bData for EPA Method 552.3 are from Tables 8, 9, 10, and 11in the method (methyl-t-butyl ether extraction).cData for EPA Method 515.4 are from Tables 7, 8, 9, and 10 in the method.dData for EPA Method 557 are from Tables 9 and 10 in the method.eMatrix: SW = drinking water from a surface water source; GW = drinking water from a ground water sourcefWhen two concentrations are listed on oneline, the first number isthe background concentration and the second indicates thefortification concentration. Asingle concentration representsthe fortification concentrationand indicates there was no detectablebackground concentration of the analyte.gRSD = relative standard deviationof seven or more replicates.Page 5 of 5Table 3. Precision and Accuracy Comparison between EPA Method 552.2 and EPA Method 557 for Dalapon in DrinkingWater—Measured in High Ionic Strength Matrix.EPA Method 552.2, Rev 1.0aEPA Method 557bConcentrationc(μg/L)% Recovery(RSD)dFortification μg/L% Recovery (RSD)0.675 + 2.0 85.8 (11)1.0 113 (4.5)15 93.2 (6.6)aData for EPA Method 552.2 are from Table 6 in the method. Matrix: tap water (groundwater source), hardness of 460 mg/L ascalcium carbonate (CaCO3). The matrix contained low concentrations of HAAs prior to fortification.bData EPA Method 557 are from Table 8 in themethod. Matrix: synthetic sample matrix prepared in reagent water with the additionof 100 mg/L ammonium chloride, 20 mg/L nitrate anion, 150 mg/L bicarbonate anion,250 mg/L chloride anion, 250 mg/L sulfateanion. The matrix did not contain HAAs before the fortification.cThe first number is the background concentration and thesecond number indicates the fortification concentration.dRSD = relative standard deviationof seven or more replicates.