Liquid chromatography—electrospray ionization ion trap mass spectrometry for analysis of mesocarb and its metabolites in human urine

A method is described for the determination of metabolites of mesocarb in human urine by combining gradient liquid chromatography and electrospray ionization (ESI)—ion trap mass spectrometry. Seven metabolites (two isomers of hydroxymesocarb, p-hydroxymesocarb, two isomers of dihydroxymesocarb and two isomers of trihydroxymesocarb) and parent drug were detected in human urine after the administration of a single oral dose 10 mg of mesocarb (Sydnocarb®, two tablets of 5 mg). Various extraction techniques (free fraction, enzyme hydrolyses and acid hydrolyses) and their comparison were carried out for investigation of the metabolism of mesocarb. After extraction procedure the residue was dissolved in methanol and injected into the column HPLC (Zorbax® SB-C18 (Narrow-Bore 2.1×150 mm i.d., 5 μm particles)) with mobile phase (0.2 ml/min) of methanol/0.2 mM ammonium acetate. Conformation of the results and identification of all metabolites are performed by LC-MS and LC-MS/MS. The major metabolites of mesocarb in urine of the human were p-hydroxylated derivative of the phenylcarbamoyl group of the parent drug (p-hydrohymesocarb) and dihydroxylated derivative of mesocarb (two isomers of dihydroxymesocarb). This analytical method for dihydrohymesocarb was very sensitive for discriminating the ingestion of mesocarb longer than the parent drug or other metabolites in human urine. The dihydroxymesocarb was detected in urine until 168–192 h after administration of the drug.