Determination of the metabolites of the herbicide dimethyl tetrachloroterephthalate in drinking water by high-performance liquid chromatography with gas chromatography/mass spectrometry confirmation.

Two metabolites of the herbicide dimethyl tetrachloroterephthalate, (DCPA), monomethyl tetrachloroterephthalate (MM) and tetrachloroterephthalic acid (TCPA), are assayed via high-performance liquid chromatography with ion paring. Samples are analyzed via direct injection, without preparation, and analyte detection is accomplished with an ultraviolet photodiode array detector. The metabolites are extracted from positive samples with a petroleum ether/diethyl ether mixture, derivatized with N,O-bis(trimethylsilyl) trifluoracetamide, and confirmed by way of gas chromatography/mass spectrometry. The HPLC analysis of 200 spiked drinking water samples yielded a recovery range of 92-106% with a mean recovery of 101% for TCPA and a recovery range of 92-101% with a mean recovery of 96% for MM. The minimum detection limits for TCPA and MM were 2.4 and 2.7 micrograms/L, respectively. In addition, the GC/MS analysis of spiked reagent water yielded mean recoveries of 91% for MM and 86% for TCPA. Twenty drinking water samples were split and analyzed by the HPLC and GC/MS methods and by USEPA Method 515.1. Comparable results were obtained. The HPLC method, which is amenable to automation, typically allows for the analysis of up to 40 samples overnight.