During drinking water disinfection with chlorine, chloramine, or ozone, potentially toxic halogenated byproducts can be formed. The disinfectants can react with naturally occurring bromide and/or organic matter in the source water and form one of the most common disinfection byproducts (DBPs): haloacetic acids (HAAs).

HAAs are highly toxic water-soluble compounds. Mono- to tri-halogenated acetic acids mainly contain bromine and/or chlorine. To protect human health, their maximum tolerable levels in drinking waters are regulated. Currently the EPA states a maximum contamination level of 60 μg/L for drinking water (EPA 816-F-09-004) for five HAAs («HAA5»): dichloroacetic acid (0 mg/L), trichloroacetic acid (20 μg/L), monochloroacetic acid (70 μg/L), with both bromoacetic and dibromoacetic acid having no defined contamination levels.

EPA Method 557 specifies the analysis of HAAs by ion chromatography coupled to mass spectroscopy (IC-MS) with LODs varying from 0.02–0.11 μg/L. In this manner, the HAAs can be separated and determined at the required low levels due to an increased sensitivity by mass detection. Even with single MS, a high sensitivity is achieved to determine the current MCLs within an adequate accuracy.

Spiked and unspiked mineral water samples are measured to simulate contaminated water sources. The samples are spiked with the following components in varying concentrations: bromate, chlorite, monochloroacetic acid (MCAA), monobromoacetic acid (MBAA), bromochloroacetic acid (BCAA), bromodichloroacetic acid (BDCAA), dibromoacetic acid (DBAA), dichloroacetic acid (DCAA), tribromoacetic acid (TBAA), chlorodibromoacetic acid (CDBAA), and trichloroacetic acid (TCAA). Recoveries are calculated by comparing spiked and unspiked sample equivalents. All samples are stabilized with ammonium chloride.

The separation of nine HAAs is performed in less than 40 minutes. Figure 2 shows the separation of the five relevant HAAs for EPA 816-F-09-004, often named as «HAA5». The spiking tests exhibit acceptable recoveries within a range of 74–124%. The estimated limits of detection are well within the EPA requirements for EPA method 557 regarding MCAA and MBAA (0.2 and 0.064 μg/L, respectively). To achieve a higher sensitivity for the other compounds, hyphenation with a triple quadrupole MS is mandatory and can be used to entirely fulfill EPA 557. However, the recent maximum contamination levels for drinking water (EPA 816-F- 09-004) for the five HAAs (DCAA, TCAA, MCAA, MBAC, and DBAA) are in sum 60 μg/L. Compared to the estimated LODs (Table 1), these are two orders of magnitude lower, showing the suitability of the present single quadrupole IC-MS method for drinking water quality measurements.