Fungicide residues in vegetables (benomyl, carbendazim, thiabendazole) are analyzed through a clean-up procedure that
uses a portion of the aqueous acetone extract prepared for multiresidue methodology. A portion of the aqueous acetone
extract (equivalent to 5 g of vegetables) is loaded onto an Extrelut-20 cartridge (the cartridge is filled with a coarse,
large-pore diatomaceous material). Then, acetone is partially removed by an upward stream of nitrogen at 2 l /min for 30
min. Benzimidazolic fungicides are recovered by percolating the cartridge with 100 ml of 0.1 M phosphoric acid solution,
which also serves to convert benomyl to carbendazim. The percolating acid solution is drained on-line through a strong
cation-exchange (SCX) solid-phase extraction cartridge with the aid of a slight vacuum. Benzimidazolic fungicides are
retained on the SCX cartridge. The phosphoric acid solution is discarded together with the washings of the SCX cartridge,
i.e., water followed by methanol–water (75:25), that remove unwanted coextractives. Finally, benzimidazolic fungicides are
recovered by eluting the SCX cartridge with methanol–ammonium formate buffer (75:25). The final extract is then analyzed
by reversed-phase HPLC with UV detection. Recoveries from crops such as apples, lettuce, strawberries and citrus fruits are
generally greater than 80% and no interferences were observed. The clean-up is simple and straightforward, requires only
disposable items, water solutions and a few milliliters of solvent and a minimum number of manipulations, and does not
require concentration steps or electrical equipment. Ó 1999 Elsevier Science B.V. All rights reserved.