An LC/MS/MS Method for Improved Quantitation of the Bound Residues in the Tissues of Animals Orally Dosed with [14C]Benomyl

Livers of goats orally dosed with [phenyl(U)-14C]benomyl contained radioactive residues which were not extractable using conventional, solvent-based extraction methods. We report a new residue method capable of enhanced extraction of benomyl-derived residues with selective and sensitive quantitation...

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Bibliographic Details
Published in:Journal of agricultural and food chemistry 2000-11, Vol.48 (11), p.5195-5199
Main Authors: Moghaddam, Mehran F, Trubey, Richard K, Anderson, Jeffrey J
Format: Article
Language:English
Subjects:
Administration, Oral
Animals
Benomyl - administration & dosage
Benomyl - pharmacokinetics
Benzimidazoles - analysis
Biological and medical sciences
Calibration
Carbamates
Carbon Radioisotopes
Chromatography, High Pressure Liquid - methods
Chromatography, Liquid - methods
Drug Residues - analysis
Female
Food industries
Food toxicology
Fundamental and applied biological sciences. Psychology
Fungicides, Industrial - administration & dosage
Fungicides, Industrial - pharmacokinetics
Goats
Liver - chemistry
Liver - metabolism
Mass Spectrometry - methods
Radioisotope Dilution Technique
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Summary:Livers of goats orally dosed with [phenyl(U)-14C]benomyl contained radioactive residues which were not extractable using conventional, solvent-based extraction methods. We report a new residue method capable of enhanced extraction of benomyl-derived residues with selective and sensitive quantitation capability for methyl 4-hydroxybenzimidazol-2-ylcarbamate (4-HBC), methyl 5-hydroxybenzimidazol-2-ylcarbamate (5-HBC), and methyl benzimidazol-2-ylcarbamate (MBC). This method involves rigorous Raney-nickel reduction of hypothesized thioether bonds between benomyl residues and polar cellular components. Following acidic dehydration (desulfurization), the polar benomyl-derived residues are extracted into ethyl acetate and analyzed by LC/MS/MS. We have shown this method to be superior to alternative extraction approaches. When applied to goat liver tissue containing [phenyl(U)-14C]benomyl-bound residues, the extraction efficiency of total radioactive residues was approximately 30%, and the major benomyl-derived residue was 5-HBC (91−95% of extractable residue) with minor levels of carbendazim (MBC) (5−9%). HPLC/LSC data were consistent with the LC/MS/MS data. The overall method satisfies U.S. regulatory requirements in extraction efficiency, selectivity in detection, and limits of quantitation for benomyl-bound residues. Keywords: Benomyl; benzimidazole; carbendazim; desulfurization; fungicide; mass spectrometry; metabolite; pesticide; Raney-nickel
ISSN:0021-8561
1520-5118
DOI:10.1021/jf991253i