Guidelines for Canadian Drinking Water Quality: Guideline Technical Document - Haloacetic Acids

6.0 Analytical methods

HAAs are relatively non-volatile and hydrophilic organic compounds. These properties make common analytical methods (e.g., purge and trap, headspace and liquid-liquid extraction) less effective for HAA separation. To facilitate analysis using gas chromatography with electron capture detector (GC/ECD), these acids must be chemically converted into methyl esters (methylated HAAs).

Three U.S. EPA methods (EPA Method 552.1, EPA Method 552.2 and EPA Method 552.3) are approved for measuring HAA5 in drinking water (U.S. EPA, U.S. EPA, 1992, 1995, 2003d). Method detection limits (MDLs) for these methods vary depending on the analyte being measured, as outlined in Table 6. The U.S. EPA also recognizes American Public Health Association (APHA) Standard Method 6251B (APHA et al., 2005) as being equivalent to the U.S. EPA standard methods for measuring HAA5 in drinking water (U.S. EPA, 2003a). All methods include sample extraction, methylation and GC/ECD analysis (using a capillary GC/ECD) steps.

EPA Method 552.1 (U.S. EPA, 1992) employs solid-phase extraction via ion exchange resins. EPA Method 552.2 (U.S. EPA, 1995) and APHA Standard Method 6251B (APHA et al., 2005) both employ micro liquid-liquid extraction with methyl tert-butyl ether (MTBE) at acidic conditions. Sodium sulphate and sulphuric acid are added to samples to increase extraction efficiency. EPA Method 552.3 (U.S. EPA, 2003e) provides the option of performing an acidic extraction using either MTBE or tertiary amyl methyl ether (TAME) before adding acidic methanol to the extract, followed by heating.

The MDLs and practical quantitation limits (PQLs) for the various methods are summarized in Table 6.

Table 6: Method detection limits and practical quantitation limits for the various methods for analysis of HAAs

	EPA Method 552.1		EPA Method 552.2		EPA Method 552.3		APHA Standard Method 6251B
Analyte	MDL (µg/L)a	PQL (µg/L)	MDL (µg/L)b	PQL (µg/L)	MDL (µg/L)c	PQL (µg/L)	MDL (µg/L)d	PQL (µg/L)
a Hodgeson and Becker (1992). b Munch et al. (1995). c U.S. EPA, (2003e). d APHA et al., (2005).
MCA	0.21	2	0.273	2.5	0.17	1.7	0.082	1
DCA	0.45	5	0.242	2.5	0.020	0.2	0.054	0.6
TCA	0.07	0.7	0.079	0.8	0.019	0.2	0.054	0.6
MBA	0.24	2	0.204	2	0.027	0.3	0.087	0.5
DBA	0.09	1	0.066	0.7	0.012	0.1	0.065	0.6