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 direct-injection 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-and-comment 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 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.

1Maximum Contaminant Level (MCL).  Source:  40 CFR 141.61(c).

2Approved methods promulgated in the drinking water regulations at 40
CFR 141.24(e)(1).



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 published

 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 column/secondary confirmation
column.

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

f Data for EPA Method 557 are from Tables 5 and 6 in the method.

Table 2.	Precision and Accuracy Comparison between EPA Methods 552.2,
552.3, 515.4, and 557 for Dalapon in Drinking Water.

Matrixe	EPA 552.2 Rev 1.0a	EPA 552.3 Rev 1.0b	EPA 515.4 Rev 1.0c	EPA
557d

	Concf (µg/L)	%Recovery (RSD)g	Concf (µg/L)	%Recovery (RSD)g	Concf
(µg/L)	%Recovery (RSD)g	Concf (µg/L)	%Recovery (RSD)g

SW	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)

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 indicates the fortification
concentration.  A single concentration represents the fortification
concentration and indicates there was no detectable background
concentration of the analyte.

g RSD = relative standard deviation of seven or more replicates.

Table 3.	Precision and Accuracy Comparison between EPA Method 552.2 and
EPA Method 557 for Dalapon in Drinking 		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 of 460 mg/L as 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 water with the addition of 100 mg/L
ammonium chloride, 20 mg/L nitrate anion, 150 mg/L bicarbonate anion,
250 mg/L chloride anion, 250 mg/L sulfate 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 concentration.

d RSD = relative standard deviation of seven or more replicates.

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