Soil column extraction followed by Liquid Chromatography Electrospray Ionization Mass Spectrometry for the efficient determination of aryloxyphenoxypropionic herbicides in soil samples at ppb 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)