Analysis of pesticides in water with liquid chromatography/atmospheric pressure chemical ionization mass spectrometry

LC/APCI/MS was used as a multiresidue analytical method for determining the thermolabile and/or polar pesticides in treated water and its raw water for water supply, which are not amenable to a routine GC/MS procedure. Of the 31 thermolabile and/or polar pesticides including 14 neutral or basic pesticides and 17 acidic ones used in this study, the detection limits for neutral/basic pesticides detected in positive-ion mode ranged from 10 to 50 μg/l and the limits for acidic pesticides detected in negative-ion mode ranged from 50 to 250 μg/l except for dicamba (500 μg/l) and benazolin (1000 μg/l). The structural information was significantly improved through an in-source collision-induced decomposition (CID) process. The solid-phase extraction (SPE) procedure, which used a special cartridge with its upper part filled with polystyrene/divinylbenzene and the lower part filled with carbon molecular sieve, was developed for extraction of the pesticides. The extraction recoveries of the pesticides were found to be higher than 72% in treated water and 67% in raw water except for thiophanatemethyl and sethoxydim, which were impossible to recover from treated water and raw water and were recovered at a recovery of 60 and 64%, respectively, in distilled water. When the multiresidue analytical method was applied to field analysis for Niigata public waterworks treatment plant in Japan, 8 pesticides were detected in treated water and 10 ones in its raw water.