Automated method for cleanup and determination of benomyl and thiabendazole in table-ready foods

An automated solid-phase extraction (SPE) cleanup with on-line liquid chromatographic (LC) analysis was developed to determine residues of benomyl (as carbendazim) and thiabendazole in table-ready food items from the U.S. Food and Drug Administration Total Diet Study (TDS). A strong-cation-exchange cleanup of an acetone extract replaces the methylene chloride solvent partitioning steps in the procedure described in the Pesticide Analytical Manual (PAM). LC analysis is accomplished with a C8 analytical column and tandem fluorescence and UV detection. Recoveries of both analytes from 32 representative TDS foods fortified at 0.05 and 0.5 microgram/g were determined. Method precision was evaluated with triplicate recovery assays on 11 foods fortified at both levels. Accuracy was tested further by assaying 47 foods for incurred residues in parallel with the validated PAM procedure for comparison, and good agreement was found. The automated SPE method reduces solvent consumption, analysis time, and labor.