Analysis of thermolabile and polar pesticides in environmental water with capillary chromatography-frit-fast atom bombardment mass spectrometry

Capillary LC/Frit-FAB-MS was used for the determination of 24 thermolabile and polar pesticides including 9 neutral/basic and 15 acidic ones which are not amenable to routine GC/MS. The base ions of acidic pesticides in negative mode were a deprotonated molecular ion except for asulam, MCPB, 2,4-DB, and warfarin, and those for neutral/basic pesticides and asulam in positive mode were a protonated one. More than one diagnostic ion were obtained except for hymexazol and bentazone. High sensitivity was obtained for neutral/basic pesticides and asulam by adopting a mobile phase composed of CH₃CN and 0.1% acetic acid, while for the other acidic pesticides, a mobile phase composed of CH₃CN and 5 mM din-butylammonium acetate (pH=6.7) was effective. The detection limits of the pesticides were in the range of 10∼300 μg/l, except for benazolin whose limit was 1000 μg/l. Environmental samples (1 L) were taken from raw water for water supply and applied to analysis after concentration by using a solid phase extraction method. 0.2 μg/l dymron (in full-scan mode) and 0.05 μ/l 2,4-D (in selected ion monitoring mode) were detected in a sample, which indicated that the LC-frit-FAB-MS method could be used for determining thermolabile and polar pesticides in environmental water with relatively high sensitivity.