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Office of Ground Water and Drinking Water 

November 19, 2012

MEMORANDUM 

SUBJECT: Basis for Expedited Approval of EPA Method 524.4

FROM: Glynda Smith, Chemist

Steve Wendelken, Chemist

Technical Support Center 

TO: The Record 

Research is complete on EPA Method 524.4 for determination of volatile organic 

contaminants in drinking water. This memo documents the comparison of Method 524.4

to EPA Method 524.2 which was promulgated for the same contaminants (see Table 1). 

It also compares Method 524.4 to EPA Method 524.3 which was approved via expedited 

method approval action (74 FR 38348). Method 524.3 was evaluated against EPA 

Method 524.2 and found to be equally as effective as the approved method. 

EPA has established Maximum Contaminant Levels (MCLs) for the 29 analytes listed in 

Table 1. The performance characteristics of EPA Method 524.4 were compared to the 

characteristics of the approved method 524.2 for these regulated analytes. The 

performance characteristics presented in this memo include detection limit as defined in 

40 CFR Part 136 Appendix B, and comparative precision and accuracy data.

Method 524.4 features most of the same elements that were incorporated in the 524.3 

revision: the list of analytes includes fuel oxygenates and volatile organic compounds 

(VOCs) amenable to purge-and-trap from the preliminary Contaminant Candidate List 3 

(CCL3). It employs ascorbic acid and maleic acid (a common food preservative) to 

dechlorinate and preserve samples, eliminating the requirement to ship a hazardous 

reagent (hydrochloric acid) to the field. Storage stability was demonstrated under the 

preservation conditions developed for Method 524.3, and these are documented in the 

524.4 revision. The primary difference between methods 524.3 and 524.4 lies in the 

purge gas. The cost of helium continues to rise and Method 524.4 was developed using 

less expensive nitrogen to purge the analytes from the water sample instead of helium.

Both methods 524.3 and 524.4 include the option for operating the mass spectrometer in 

selected ion monitoring (SIM) mode to achieve lower detection limits. As opposed to 

Method 524.3, the Method 524.4 SIM data failed to meet the detection limits required for 

determining monitoring frequencies for 1,2-dibromo-3-chloropropane (DBCP) and 1,2-

dibromoethane (EDB). In order to be considered for expedited approval, methods must 

be equally as effective as those approved in the regulations. As cited in 40 CFR 

141.24(e)(1), the approved methods for DBCP and EDB are 504.1 and 551.1. Relative to 
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those approved methods, 524.4 cannot be considered equally as effective in terms of 

meeting the detection criteria. Therefore, methods 524.4 cannot be approved for 

compliance monitoring of DBCP or EDB. 

Table 2 provides a comparison of detection limits excerpted from the method 

performance sections of the approved method 524.2, along with methods 524.3 and 

524.4. The detection levels for Method 524.4 (both full scan and SIM) are similar to 

those obtained by the approved method, except as described above for EDB and DBCP. 

The Code of Federal Regulations (40 CFR 141.24 (f)(17)) requires laboratories to meet a 

minimum detection limit (MDL) of 0.5 μg/L for the contaminants listed in 40 CFR 

141.61 (a), (chemicals generally referred to as volatile organic contaminants - VOCs) in 

order to be certified. It is demonstrated in Table 2 that this requirement is easily met 

using Method 524.4 for all of the regulated VOCs. Regulatory detection levels for 

determining monitoring frequencies (not laboratory certification) for DBCP and EDB are 

published at 40 CFR 141.24(h)(18). As discussed previously, the reported data indicate 

that these levels are not met using Method 524.4. Minimum Reporting Level (MRL) 

requirements for laboratory certification and reporting purposes are published at 40 CFR 

141.131(b)(2)(iv) for the Trihalomethanes (chloroform, bromodichloromethane, 

dibromochloromethane, and bromoform). These levels are easily met using Method 

524.4.

A comparison of precision and accuracy data obtained in full scan mode for the approved 

method 524.2, Method 524.3, and Method 524.4 are presented in Table 3. The data were 

obtained by fortifying reagent water samples with the contaminants and performing 

replicate analyses. The accuracy (as shown by percent Recovery—%R) and precision 

(relative standard deviation—RSD) data for Method 524.4 are comparable to the other 

two methods. 

In summary, the performance characteristics of EPA Method 524.4 are within the range 

of the characteristics obtained using the promulgated method for the same contaminants. 

Therefore, EPA Method 524.4 is equally as effective as the promulgated method for 

determining the concentrations of VOCs and TTHM regulated in drinking water.
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Table 1. Method 524.4 Analytes Regulated in Drinking Water, Maximum Contaminant Levels, and Approved Methods.

Approved 

Method

Method 524.3 – Operation 

Mode

Method 524.4 – Operation 

Mode

Analyte CAS No. MCL, μg/L a 524.2

Rev 4.1

Full Scan Selected Ion 

Monitoring

Full Scan Selected Ion 

Monitoringd

1 1,1,1-trichloroethane 71-55-6 200 X X X X

2 1,1,2-trichloroethane 79-00-5 5 X X X X

3 1,1-dichloroethene 75-35-4 7 X X X X

4 1,2,4-trichlorobenzene 120-82-1 70 X X X X

5 1,2-dibromo-3-chloropropane 96-12-8 0.2 X X

6 1,2-dibromoethane 106-93-4 0.05 X X

7 1,2-dichlorobenzene 95-50-1 600 X X X X

8 1,2-dichloroethane 107-06-2 5 X X X X

9 1,2-dichloropropane 78-87-5 5 X X X X

10 1,4-dichlorobenzene 106-46-7 75 X X X X

11 benzene 71.43-2 5 X X X X

12 bromodichloromethane 75-27-4 80 TTHM b X X X X

13 bromoform 75-25-2 80 TTHM b X X X X

14 carbon tetrachloride 56-23-5 5 X X X X

15 chlorobenzene 108-90-7 100 X X X X

16 chloroform 67-66-3 80 TTHM b X X X X

17 cis-1,2-dichloroethene 156-59-2 70 X X X X

18 dibromochloromethane 124-48-1 80 TTHM b X X X X

19 ethylbenzene 100-41-4 700 X X X X

20 methylene chloride 75-09-2 5 X X X X

21 m-xylene (co-elutes w/para) 108-38-3 10,000 c X X X X

22 o-xylene 95-47-6 10,000 c X X X X

23 p-xylene (co-elutes w/meta) 106-42-3 10,000 c X X X X

24 styrene 100-42-5 100 X X X X

25 tetrachloroethene 127-18-4 5 X X X X

26 toluene 108-88-3 1000 X X X X

27 trans-1,2-dichloroethene 156-60-5 100 X X X X

28 trichloroethene 79-01-6 5 X X X X

29 vinyl chloride 75-01-4 2 X X X X

a. MCL = Maximum Contaminant Level; 40 CFR 141.61(a) for volatile organic contaminant MCLs; 40 CFR 141.61(c) for 1,2-dibromo-3-chloropropane (DBCP) and 1,2-dibromoethane 

(EDB) MCLs; and 40 CFR 141.64(b) for TTHM MCL.

b. TTHM = Total Trihalomethanes (sum of chloroform, bromodichloromethane, dibromochloromethane, and bromoform)

c. Regulated as xylenes (total) (sum of o-xylene, m-xylene, and p-xylene)

d. Additional multi-lab Selected Ion Monitoring data obtained for Method 524.4 (DLs and LCMRLs)
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 Table 2. Detection Limit Comparison between Approved Method 524.2, Expedited Approval Method 524.3 and Method 524.4 for 

Purgeable Organic Compounds Regulated in Drinking Water. (All concentrations are μg/L.)

Analyte

Regulatory 

Detection 

Limit a

524.2

Rev 4.1 

MDLs b

524.3 

Full Scand

MDLs/LCMRLs c

524.3 

SIM e

MDLs/LCMRLs

524.4

Full Scan g

MDLs/LCMRLs

524.4

SIM h

MDLs/LCMRLs

524.4 SIM i

Multi-Lab

MRLs

1 1,1,1-trichloroethane 0.5 0.08 0.026 / 0.076 --- 0.060/0.17 0.009/0.039 ---

2 1,1,2-trichloroethane 0.5 0.10 0.048 / 0.14 --- 0.048/0.38 0.010/0.029 ---

3 1,1-dichloroethene 0.5 0.12 0.049 / 0.092 --- 0.14/0.18 0.009/0.061 ---

4 1,2,4-trichlorobenzene 0.5 0.04 0.013 / 0.053 --- 0.071/0.15 0.013/0.030 ---

5 1,2-dibromo-3-chloropropane 0.02 0.26 f 0.063 f / 0.27 f 0.0016 / 0.0017 0.15 f

/0.44 f 0.033 f/0.069 f 0.060 f

6 1,2-dibromoethane 0.01 0.06 f 0.018 f / 0.059 f 0.0010 / 0.0041 0.090 f

/0.13 f 0.023 f/0.048 f 0.020 f

7 1,2-dichlorobenzene 0.5 0.03 0.019 / 0.066 --- 0.056/0.14 0.013/0.025 ---

8 1,2-dichloroethane 0.5 0.06 0.025 / 0.051 --- 0.027/0.23 0.012/0.029 0.017

9 1,2-dichloropropane 0.5 0.04 0.018 / 0.065 --- 0.088/0.17 0.011/0.043 0.067

10 1,4-dichlorobenzene 0.5 0.03 0.015 / 0.065 --- 0.029/0.19 0.012/0.026 ---

11 benzene 0.5 0.04 0.017 / 0.030 --- 0.028/0.11 0.012/0.022 0.055

12 bromodichloromethane 1.0 0.08 0.014 / 0.073 --- 0.081/0.19 0.011/0.027 ---

13 bromoform 1.0 0.12 0.040 / 0.15 --- 0.14/0.26 0.008/0.021 ---

14 carbon tetrachloride 0.5 0.21 0.044 / 0.098 --- 0.073/0.14 0.008/0.033 0.018

15 chlorobenzene 0.5 0.04 0.019 / 0.15 --- 0.050/0.20 0.009/0.036 ---

16 chloroform 1.0 0.03 0.025 / 0.054 --- 0.070/0.16 0.015/0.032 ---

17 cis-1,2-dichloroethene 0.5 0.12 0.042 / 0.12 --- 0.083/0.21 0.037/0.040 ---

18 dibromochloromethane 1.0 0.05 0.027 / 0.14 --- 0.10/0.23 0.006/0.016 ---

19 ethylbenzene 0.5 0.06 0.010 / 0.085 --- 0.026/0.15 0.009/0.013 ---

20 methylene chloride 0.5 0.03 0.14 / 0.25 --- 0.18/0.15 NA ---

21 m-xylene (co-elutes w/para) 0.5 0.05 0.020 / 0.069 --- 0.11/0.30 0.020/0.17 ---

22 o-xylene 0.5 0.11 0.010 / 0.039 --- 0.11/0.26 0.016/0.037 ---

23 p-xylene (co-elutes w/meta) 0.5 0.13 0.020 / 0.069 --- 0.11/0.30 0.020/0.17 ---

24 styrene 0.5 0.04 0.011 / 0.11 --- 0.033/0.20 0.012/0.018 ---

25 tetrachloroethene 0.5 0.14 0.036 / 0.081 --- 0.059/0.27 0.011/0.025 0.018

26 toluene 0.5 0.11 0.024 / 0.053 --- 0.031/0.13 0.009/0.034 ---

27 trans-1,2-dichloroethene 0.5 0.06 0.050 / 0.098 --- 0.12/0.29 0.014/0.028 ---

28 trichloroethene 0.5 0.19 0.035 / 0.091 --- 0.078/0.13 0.012/0.037 0.020

29 vinyl chloride 0.5 0.17 0.029 / 0.092 --- 0.063/0.15 0.007/0.048 0.026

a. Method detection limit (MDL) requirement for laboratory certification purposes published at 40 CFR 141.24(f)(17) for volatile organic contaminants; regulatory detection level for 

determining monitoring frequencies published at 40 CFR 141.24(h)(18) for 1,2-dibromo-3-chloropropane and 1,2-dibromoethane; Minimum Reporting Level (MRL) requirements for 

laboratory certification and reporting purposes published at 40 CFR 141.131(b)(2)(iv) for chloroform, bromodichloromethane, dibromochloromethane, and bromoform.

b. MDL calculated according to procedure published at 40 CFR 136 Appendix B. Data sources: Method 524.2 Table 4

c. Lowest Concentration Minimum Reporting Level (LCMRL) 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.

d. Method 524.3 Table 6
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e. Method 524.3 Table 10

f. Method fails to meet regulatory requirement for this contaminant

g. Method 524.4 Table 6

h. Method 524.4 Table 10

i. EPA Method 524.4 Multi-Lab SIM MRL determination for possible inclusion in a carcinogenic VOC group; internal communication

Table 3. Precision and Accuracy Comparison in Fortified Reagent Water between Approved Method 524.2, Expedited Method 524.3, 

and Method 524.4 using Full Scan MS Detection

Analyte 524.2 Rev. 4.1 a 524.3 - Full Scan e 524.4 – Full Scan f

C b %R c RSD d C b %R c RSD d C b %R c RSD d

1 1,1,1-trichloroethane 0.5-10 98 8.1 1.0 98.0 10 1.0 91.1 6.3

2 1,1,2-trichloroethane 0.5-10 104 7.3 1.0 101 7.3 1.0 101 8.5

3 1,1-dichloroethene 0.1-10 94 6.7 1.0 94.8 9.0 1.0 93.2 5.3

4 1,2,4-trichlorobenzene 0.5-10 108 8.3 1.0 95.6 7.2 1.0 91.9 2.1

5 1,2-dibromo-3-chloropropane 0.5-10 83 19.9 1.0 99.3 8.2 1.0 90.9 7.1

6 1,2-dibromoethane 0.5-10 102 3.9 1.0 101 7.9 1.0 89.5 4.5

7 1,2-dichlorobenzene 0.1-10 93 6.2 1.0 96.3 8.3 1.0 96.6 3.4

8 1,2-dichloroethane 0.1-10 95 5.4 1.0 101 7.4 1.0 102 4.5

9 1,2-dichloropropane 0.1-10 97 6.1 1.0 99.6 8.9 1.0 92.4 6.0

10 1,4-dichlorobenzene 0.2-20 103 6.4 1.0 95.8 7.5 1.0 97.2 3.3

11 benzene 0.1-10 97 5.7 1.0 99.4 7.8 1.0 93.6 4.6

12 bromodichloromethane 0.1-10 95 6.1 1.0 97.1 8.7 1.0 97.1 3.7

13 bromoform 0.5-10 101 6.3 1.0 92.0 8.1 1.0 91.0 3.9

14 carbon tetrachloride 0.5-10 84 8.8 1.0 93.9 7.6 1.0 92.4 3.9

15 chlorobenzene 0.1-10 98 5.9 1.0 99.2 7.2 1.0 93.4 3.3

16 chloroform 0.5-10 90 6.1 1.0 99.4 5.3 1.0 97.3 4.3

17 cis-1,2-dichloroethene 0.5-10 101 6.7 1.0 99.5 8.9 1.0 94.2 5.6

18 dibromochloromethane 0.1-10 92 7.0 1.0 95.0 7.9 1.0 95.7 3.7

19 ethylbenzene 0.1-10 99 8.6 1.0 95.9 9.2 1.0 93.8 3.8

20 methylene chloride 0.1-10 95 5.3 1.0 106 5.6 1.0 84.5 15

21 m-xylene (co-elutes w/para) 0.1-10 97 6.5 1.0 98.2 9.2 1.0 93.3 2.9

22 o-xylene 0.1-31 103 7.2 1.0 98.3 8.3 1.0 94.3 2.7

23 p-xylene (co-elutes w/meta) 0.5-10 104 7.7 1.0 98.2 9.2 1.0 93.3 2.9

24 styrene 0.1-100 102 7.2 1.0 95.5 8.8 1.0 95.3 3.3

25 tetrachloroethene 0.5-10 89 6.8 1.0 98.8 8.8 1.0 87.2 5.8

26 toluene 0.5-10 102 8.0 1.0 99.2 9.6 1.0 92.0 6.5

27 trans-1,2-dichloroethene 0.1-10 93 5.6 1.0 100 6.8 1.0 104 3.2

28 trichloroethene 0.5-10 90 7.3 1.0 99.6 7.9 1.0 103 4.9

29 vinyl chloride 0.5-10 98 6.7 1.0 94.9 8.1 1.0 106 6.0

a. Method 524.2 data - Table 4

b. C = Concentration (μg/L) fortified into reagent water
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c. %R = % Recovery

d. RSD = relative standard deviation

e. Method 524.3 data - Table 7

f. Method 524.4 data – Table 7