Analyzing haloacetic acids using gas chromatography/mass spectrometry

Haloacetic acids (HAAs) are a group of disinfection by-products formed in chlorinated water. Due to their potential health effects and widespread occurrences, HAAs are regulated in drinking water in the United States under a promulgated regulation. To better control the formation of HAAs in drinking water, a reliable and accurate analytical method is needed for HAA monitoring. In the present study, a liquid-liquid microextraction, acidic methanol derivatization, and gas chromatography/mass spectrometry (GC/MS) detection method was developed for determining HAAs and dalapon in drinking water. The newly developed method is capable of analyzing all nine HAAs and dalapon at microgram/l levels. The method performance, including the method detection limit (MDL) and spiking recovery, was evaluated. In comparison to EPA Method 552.2, which uses gas chromatography/electron capture detection (GC/ECD), this GC/MS method gave cleaner baselines and had few interfering peaks. For each of all nine HAAs and dalapon, the MDL was less than 1 microgram/l and the spiking recovery ranged from 73 to 165%. Using the GC/MS method, the run time could also be significantly reduced without compromising the analytical results. Further study is needed to fine-tune this GC/MS based analytical method, especially in the detection of brominated trihaloacetic acids and monochloroacetic acid.