Determination of benzoylureas in tomato by high-performance liquid chromatography using continuous on-line post-elution photoirradiation with fluorescence detection.

A photochemically induced fluorescence post-column method, with HPLC separation and fluorescence detection, was developed for the determination of five naturally non-fluorescent benzoylurea insecticides: diflubenzuron, triflumuron, hexaflumuron, lufenuron and flufenoxuron. The applicability of the method to the determination of insecticides in spiked tomato was evaluated. Samples were extracted into ethyl acetate and further cleaned-up by solid-phase extraction using an aminopropyl-bonded silica cartridge. The interferences due to the matrix effect were eliminated using matrix matched standards. Linear dynamic ranges were established over more than two orders of magnitude. The limits of detection ranged from 5 to 21 ng ml(-1) (or 0.5 and 2.1 microg kg(-1) in the vegetable samples), with relative standard deviations lower than 5.0%, using blank tomato extract. Mean recoveries ranged from 79 to 102%.