Gas chromatographic–tandem mass spectrometric method for the quantitation of carbofuran, carbaryl and their main metabolites in applicators’ urine

A new gas chromatographic–tandem mass spectrometric method has been developed and validated for the determination of two N-methylcarbamates, carbofuran and carbaryl and their metabolites in applicators’ urine specimens. Mild conditions were used for sample preparation based on enzymic hydrolysis and solid-phase extraction using Oasis HLB sorbent cartridges. Amides, phenols and ketones were first converted to volatile derivatives of trifluoroacetic acid anhydride (TFAA) and afterwards were quantitated using tandem mass spectrometry. Linear calibration equations (1–200 ng mL−1 urine) were obtained from fortified urine samples for all eight compounds, carbaryl, 1-naphthol, 2-naphthol, and carbofuran, 3-hydroxycarbofuran, 7-phenol, carbofuran-3-keto, 3- hydroxycarbofuranphenol. For all compounds, the limit of detection was lower than 0.1 ng mL−1. Precision for all compounds, at the concentrations of 1, 10 and 100 ng mL−1 (n = 5) in-fortified urine samples ranged from 0.7% to 18%. Accuracy was calculated at two concentrations 8 and 80 ng mL−1 (n = 5) and ranged from −8.4% to 8.2%. Relative recoveries at concentrations of 1, 10 and 100 ng mL−1, ranged from 71% to 116%. The method was successfully applied to five male applicators and 10 non-applicators (including both smokers and non-smokers).