OPTIMIZATION OF HIGH PERFORMANCE LIQUID CHROMATOGRAPHY/MASS SPECTROMETRY APPARATUS FOR DETERMINATION OF IMIDAZOLINONE HERBICIDES IN SOIL AT LEVELS OF A FEW PPB

A rapid, simple and accurate method for the simultaneous determination of residues of the imidazolinone herbicides (imazapyr, imazaquin, imazamethabenz and imazamethabenz-methyl) in soil is described, The basis of the method is the formation of a supernatant by sonication of the soil with 0.1 M KCI, After removal from the soil particles, the pesticides are quantified by reversed-phase liquid chromatography/mass spectrometry with an Turboionspray interface (LC/TurboIS-MS). This is a new high flow ionspray (IS) interface developed by Sciex, A conventional 4.6 mm i.d. reversed phase LC C-18 column operating with a mobile phase flow rate of 1 mL/min, was used to chromatograph the analytes, A flow of 200 mu L/min. of the column effluent was diverted to the ISI source. The effects of acid concentration on IS-MS detector response in the mobile phase were investigated. The effects on the production of diagnostic fragments produced by varying the orifice plate voltage and the response of the MS detector were also evaluated. For the analyte considered, the response of the mass detector was linearly related to the amount of analyte injected between 1 and 50 ng, Recoveries from a variety of soil types, fortified over the range 50-200 ppb, are essentially quantitative for each imidazolinone and the detection limits (signal-to-noise ratio = 3) of the method are always lower than 14 ng/g, (C) 1998 John Wiley & Sons, Ltd.