Optimized chromatographic conditions for separation of halogenated acetic acids by ultra-performance liquid chromatography-electrospray ionization-mass spectrometry.

Emerging halogenated acetic acids (HAAs), especially mixed halogenated acids such as chlorobromo-, chloroiodo- and bromoiodo-acetic acids, are unregulated disinfection by-products in drinking water. Because these compounds are hydrophilic and strongly acidic, they are difficult to detect at trace levels using approved analytical methods. In the present study, 13 HAAs were effectively separated on three ultra-performance liquid chromatography columns. The effects of changing in the aqueous mobile phase, acidic solutions and cationic volatile ion pair reagents were investigated. The samples were pretreated by filtration, and extraction, while derivatization and concentration procedures were not required. The limits of quantitation for regulated HAAs were between 0.5 μg/L and 1.7 μg/L and for unregulated HAAs were 1.2 and 5.8 μg/L, especially for the iodinated acetic acids were 1.5 and 2.1 μg/L. The method was applied to two finished water samples collected in China (Shanghai and Xuzhou) from water treatment plants that use chlorine for disinfection. Multiple unregulated HAAs were found in the two samples, but iodoacids were only detected in the water sample from Shanghai, which could be attributed to the characteristics of the source water. The presence of unregulated HAAs, especially mixed bromo- and iodoacetic acids, in the finished water samples could affect human health, and this warrants further investigation.