Evaluation of the effects of various gas chromatographic parameters on haloacetic acids disinfection by-products analysis

Thermal decomposition of the analytes during the analysis is a problem for haloacetic acids (HAAs). We evaluated the effect of GC injection port temperature and the amount of trace water in the sample on the HAAs' analysis. For three brominated HAAs, the variation in intensity due to the change of injection port temperature was significant. The largest variation observed was tribromoacetic acid methyl ester (from 3.2 to 1 for injection port temperature changing from 170 °C to 250 °C). Tribromoacetic acid methyl ester partially decomposed to dibromoacetic acid and to tribromomethane in a competitive way. At a low injection port temperature, tribromomethane formation was preferred, but at a high injection port temperature, the debrominated methyl ester formation dominated. Water contained in the sample may accelerate the hydrolysis process of the esters in the injection port, and this effect was also the greatest for the brominated trihaloacetic acids. Direct injection of underivatized HAAs into the GC/MS indicated that brominated HAAs can be nearly quantitatively thermal decomposed to the corresponding halomethanes.