Determination of benomyl by high-performance liquid chromatography/mass spectrometry/selected ion monitoring

Methyl 1-(butylcarbamoyl)-2-benzimidazolecarbamate (benomyl) was analyzed by reversed-phase high-performance liquid chromatography/mass spectrometry/selected ion monitoring (HPLC/MS/SIM) using 2-aminobenzimidazole (2-AB) as internal standard. Benomyl was quantitatively converted to methyl 2-benzimidazolecarbamate (carbendazim) by acid hydrolysis, and the latter was recovered by partitioning into ethyl acetate. The minimum detectable level in apples, peaches, and tomatoes was 0.025 ppm. Recoveries of benomyl fortified at 0.1 ppm were in the range 85-110% in all three commodities. Twenty-five samples each of tomatoes, peaches, and apples were analyzed. Four apple samples contained levels of 0.15-0.59 ppm benomyl, while eighteen of the peach samples analyzed had levels of 0.25-3.48 ppm. Trace levels of benomyl were also found in three tomato samples and one apple sample