Analysis of chlorophenoxy acid herbicides in water by large-volume on-linederivatization and gas chromatography-mass spectrometry

This work presents a modified method to analyze chlorophenoxy acid herbicid es in water samples. The herbicides 2,4-D(2,4-dichlorophenoxyacetic acid), Silver (2,3,5-trichlorophenoxypropionic acid) and 2,4,5-T (2,4,5-trichlorop henoxyacetic acid) were used to evaluate the method. The method involves ex traction of samples by a graphitized carbon black cartridge, and on-line de rivatization in the GC injection port using a large-volume (10-20 mul) dire ct sample introduction (DSI) device with tetraalkylammonium salts. The anal ytes were then identified and quantitated by ion-trap gas chromatography-ma ss spectrometry. The large-volume DSI injection-port derivatization techniq ue provides sensitivity, fast and reproducible results for chlorophenoxy ac id herbicides residues, to quantitation at 0.1 to 0.2 mug/l in 500-ml water samples. An enhanced characteristic mass chromatogram of molecular ions of butylated chlorophenoxy acid herbicides with a significant chlorine isotop e pattern by electron impact ionization MS allows us to determine herbicide s residues at trace levels in aqueous samples. Recovery of the herbicide re sidues in spiked various water samples ranged from 70 to 99% while RSDs ran ged from 1 to 13%. (C) 2000 Elsevier Science B.V. All rights reserved.