Soil column extraction followed by liquid chromatography and electrospray ionization mass spectrometry for the efficient determination of aryloxyphenoxypropionic herbicides in soil samples at ng g-1 levels

An analytical method is described for determination of ng g(-1) levels of aryloxyphenoxypropionic herbicides in soil, which combines a simple technique for sample preparation and Liquid chromatography/electrospray ionization mass spectrometry with negative ion mode of operation. This method involves a simple treatment of the sample via isolation and trace enrichment by soil column extraction (SCE) and clean-up with a Carbograph-1 cartridge. The effects of various extractant solutions and soil type, test of extractability for aged field-treated soil and pesticide concentration on the performance of the SCE are investigated. Overall, the recoveries for each herbicide across all fortified samples (1-50 ng g(-1)) were 89+/-3.5% for fluazifop, 90+/-3.3% for haloxyfop and 89+/-3.1% for diclofop. To achieve good liquid chromatographic separation, acidification of the eluent and subsequent postcolumn addition of a neutralization buffer are needed to avoid ion signal suppression. The detection limits (S/N=3) obtained using the time-scheduled selected ion monitoring varied from 0.1 to 0.3 ng g(-1). (C) 1998 Elsevier Science B.V. All rights reserved.