Determination of regularly distributed plant protectants in raw and drinking waters, using a multiresidue method with cyclodextrin-modified micellar electrokinetic chromatography

Eighteen plant protectant compounds were separated and determined by cyclod extrin-modified micellar electrokinetic chromatography (MEKC) in a multicla ss/multiresidue method. The pesticides included are those dispersed in the greatest amounts today over agricultural acreage, and they represent 8 diff erent classes of compounds (azoles, benzoic acids, chloroacetanilides, phen oxy acids, phenylureas, sulfonylureas, thiocarbamates, and triazines) cover ing a wide range of chemical reactivities and physicochemical properties. A 500 mt sample of tap water is preconcentrated by solid-phase extraction (S PE) with 300 mg combined polystyrene-divinylbenzene and methacrylate macrop orous resins. Trapped analytes are eluted collectively with diethyl ether. Concentration and solvent change yield 250 mu L of an acetone "concentrate, " which is further worked up and concentrated 1:10 to produce the MEKC inje ction solution containing 10 mmol/L sodium dodecyl sulfate (SDS) surfactant , For MEKC, 2 phosphate/SDS buffer systems were designed, each allowing com plete separation of all pesticides in a single run. Sensitivity was enhance d by a self-etched bubble cell and an injection procedure which employs sta cking at reversed polarity. The ability of MEKC to determine plant protecta nts in raw and drinking waters at the 0.1 mu g/L level, as demanded by the guidelines of the European Union, was demonstrated with spiked tap waters. Recoveries were between 75 and 110%, and limits of quantification, evaluate d as method detection limits according to guidelines of the U.S. Environmen tal Protection Agency, ranged between 0.03 and 0.10 mu g/L. The precisions of the relative migration times were all below 0.5%.