Techniques and methods for the determination of haloacetic acids in potable water

Haloethanoic (haloacetic) acids (HAAs) are formed as disinfection byproduct s (DBPs) during the chlorination of natural water to make it rt for consump tion. Sundry analytical techniques have been applied in order to determine the concentrations of the HAAs in potable water supplies: gas chromatograph y (GC-MS, GC-ECD); capillary electrophoresis (CE); liquid chromatography (L C), including ion chromatography (IC); and electrospray ionization mass spe ctrometry (ESI-MS). Detection limits required to analyze potable water samp les can be regularly achieved only by GC-ECD and ESI-MS. Without improvemen ts in preconcentration or detector sensitivity, CE and LC will not rnd appl ication to potable water supplies. The predominant GC-ECD methods use eithe r diazomethane or acidified methanol to esterify (methylate) the carboxylic acid moiety. For HAA5 analytes, regulated under the EPA's Stage 1 DBP Rule , diazomethane is satisfactory. For HAA9 data gathered under the Informatio n Collection Rule, acidified methanol outperforms diazomethane, which suffe rs from photo-promoted side reactions, especially for the brominated trihal oacetic acids. Although ESI-MS can meet sensitivity and selectivity require ments, limited instrumentation availability means this technique will not b e widely used for the time being. However, ESI-MS can provide valuable conf irmatory information when coupled with GC-ECD in a research setting.