HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC METHOD FOR SIMULTANEOUS DETERMINATION OF RESIDUAL BENOMYL AND METHYL 2-BENZIMIDAZOLE CARBAMATE ON APPLE FOLIAGE WITHOUT CLEANUP
A simple HPLC method was developed to individually determine residues of benomyl and MBC [methyl-2-benzimidazolecarbamate] on apple leaves without cleanup. Sample leaves in a Mason jar are freeze-dried and tumbled for extraction in CHCl3 containing 5000 .mu.g n-propyl isocyanate/ml at 1.degree. C. n-Butyl isocyanate is added to the extract at 5000 .mu.g/ml, and 20 .mu.l fo the mixture is injected into the HPLC system. A Brownlee LiChrosorb silica gel column with a guard column is operated with a mixed mobile phase of chloroform-hexane (4 + 1) saturated with water. MBC, present as a degradation compound of benomyl, is identified as methyl 1-(n-propylcarbamoyl)-2-benzimidazole carbamate (MBC-n-PIC derivative). At 280 nm, both benomyl and MBC-n-PIC can be detected with UV detector at a level of 0.2 ppm in apple leaves.