OPTIMIZATION OF HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY MASS-SPECTROMETRY APPARATUS FOR DETERMINATION OF IMIDAZOLINONE HERBICIDES IN SOIL ATLEVELS OF A FEW PPB

A rapid, simple and accurate method for the simultaneous determination of residues of the imidazolinone herbicides (imazapyr, imazaquin, ima zamethabenz 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 pestic ides are quantified by reversed-phase liquid chromatography/mass spect rometry 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 phas e flow rate of 1 mL/min, was used to chromatograph the analytes, A flo w of 200 mu L/min. of the column effluent was diverted to the ISI sour ce. The effects of acid concentration on IS-MS detector response in th e mobile phase were investigated. The effects on the production of dia gnostic fragments produced by varying the orifice plate voltage and th e response of the MS detector were also evaluated. For the analyte con sidered, the response of the mass detector was linearly related to the amount of analyte injected between 1 and 50 ng, Recoveries from a var iety of soil types, fortified over the range 50-200 ppb, are essential ly quantitative for each imidazolinone and the detection limits (signa l-to-noise ratio = 3) of the method are always lower than 14 ng/g, (C) 1998 John Wiley & Sons, Ltd.