Simplified clean-up for the determination of benzimidazolic fungicides by high-performance liquid chromatography with UV detection

Abstract

A method was developed that allows the determination of benomyl, carbendazim (MBC), thiophanate methyl (TFM) as carbendazim and thiabendazole (TBZ) by HPLC with UV detection. After extraction and cyclization of TFM into MBC, the conversion of benomyl into MBC is carried out by absorbing the raw extract on a ready-to-use, disposable column of a macroporous Kieselghur-type material and percolating 0.1 M HCl through it. Benzimidazolic residues are partitioned into the acid solution whereas most of the co-extractives are retained on the column. The final clean-up is performed on a strong cation-exchange (SCX) cartridge. The determination of MBC and TBZ is carried out by HPLC-UV detection on a polymeric reversed-phase column eluted with a water-ecetonitrile (70 : 30). Recoveries of MBC and TBZ from pear, apple, orange, grape, kiwi, tomato and lettuce, spiked at levels of 0.22 and 0.88 mg/kg, were satisfactory (70%). The main features of the method include high selectivity towards MBC and TBZ, reduced consumption of reagents and solvents, reduced handling operations, lack of emulsions and the use of disposable items.