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DOES MICRO LC/MS OFFER ADVANTAGES OVER CONVENTIONAL LC/MS IN IDENTIFYING DISINFECTION BY-PRODUCTS
Citation:
Caughran, T V., S D. Richardson, F G. Crumley, AND T. Poiger. DOES MICRO LC/MS OFFER ADVANTAGES OVER CONVENTIONAL LC/MS IN IDENTIFYING DISINFECTION BY-PRODUCTS. Presented at 47th American Society for Mass Spectrometry Conference, Dallas, TX, June 13-17, 1999.
Description:
Lower maximum contaminant levels (MCLs) of disinfection by-products were set for drinking water municipalities by the Stage 1 DBP Rule in November, 1998. With these new regulations, additional water treatment plants are expected to choose alternative disinfectants to chlorine. Although alternative disinfectants are gaining in popularity, not much is known about the by-products they produce. More research is needed to comprehensively identify these DBPs, and to determine what health effects these new DBPs have compared to those produced by chlorine. Many unidentified DBPs are believed to be in the polar fraction, which cannot be easily extracted from water. By using LC/MS instead of GC/MS, detection of these highly polar compounds should be possible, whereas GC/MS is not well suited for the determination of polar compounds. Micro LC/MS has become a popular technique for the analysis of complex pharmaceuticals, industrial chemicals, and other natural products. In those cases, it has offered lower detection levels (1). To our knowledge, the micro LC/MS technique has not been applied to the identification of drinking water disinfection by-products, which are typically present at low levels (ng/L-ug/L). In order to identify all possible polar DBPs in a drinking water mixture, our research group has conducted a study to determine whether the performance of a micro LC/MS system is superior to a conventional HPLC/MS system. In this study, a Fisons Platform quadrupole mass spectrometer was chosen as the detector, a Hewlett Packard 1050 HPLC system was used as the conventional HPLC, and a Microtech Ultra Plus system was chosen as the micro LC component. A series of standards, samples from drinking water plants in metropolitan Atlanta, and in Israel were analyzed. Other advantages and disadvantages of a micro LC/MS system over a conventional LC/MS system will be presented. The micro LC/MS system appears to produce a factor of 2x greater sensitivity compared to the conventional LC/MS system, and produced lower chemical background levels. However, reconstructed ion chromatograms are still necessary to observe the chromatographic peaks of the low-level DBPs.