Determination of phenylurea herbicide residues in vegetables by liquid chromatography after gel permeation chromatography and Florisil cartridge cleanup.

A liquid chromatographic method for quantitative determination of 9 phenylurea herbicide residues (metoxuron, metobromuron, monolinuron, chlortoluron, isoproturon, diuron, linuron, chloroxuron, and neburon) in potatoes, carrots, and mixed vegetables is described. Samples are extracted with acetone, partitioned with ethyl acetate-cyclohexane (50 + 50, v/v) and cleaned up by gel permeation chromatography with ethyl acetate-cyclohexane (50 + 50, v/v) as eluant. A small column (1 cm id) packed with Biobeads SX3 resin is used to reduce solvent consumption and analytical time. After solid-phase extraction on a Florisil cartridge, herbicide residues are successfully separated on a C18 column by gradient elution and determined by UV detection at 242 nm. Average recoveries of 9 compounds from different samples range from 70 to 98% at 0.010 and 0.100 mg/kg fortification levels. Quantitation limits are 0.010 mg/kg.