Gas Chromatographic and Mass Spectrometric Determination of Asulam, Mecoprop and Trichlorfon in Water Sample

A simultaneous analytical procedure was devised for asulam as a carbamate herbicide, trichlorfon (DEP) as an organophosphorus pesticide and mecoprop (MCPP) as a phenoxy-acid herbicide in tap water and their source. Owing to the thermolability of DEP and the lower volatility of asulam and MCPP, detection in GC/MS is difficult. To raise the efficacy of GC/MS, the pesticide mixture was first methylated, followed by heptafluorobutylation. For asulam, the secondary amino and primary amino groups were methylated and heptafluorobutylated, respectively. Carboxyl group of MCPP was methylated, and hydroxyl group of DEP was heptafluorobutylated. Using Sep-pak PS-1 as the solid phase extraction tube, we carried out extraction of the pesticides from water samples and their condensation. A recovery test on surface water was performed to prove the method works even at a low level (2 μg/l) of the pesticides.