Simultaneous analysis of herbicide metribuzin and its transformation products in tomato using QuEChERS-based gas chromatography coupled to a triple quadrupole mass analyzer

A sensitive and simple method for the quantification of metribuzin and its major transformation products in tomato using QuEChERS-based gas chromatography coupled to a triple quadrupole mass analyzer (GC-MS/MS) with multiple reactions monitoring (MRM) was developed and validated. Residues of metribuzin, desamino-metribuzin (DA), diketo-metribuzin (DK), and desamino-diketo-metribuzin (DADK) were extracted from tomato by acetonitrile and purified by graphitized carbon black (GCB) and primary secondary amine (PSA). All analytes gave high correlation coefficients (r2) above 0.995, and the limits of detection (LOD) ranged from 0.002 to 0.008 mg/kg. The mean recoveries of the analysis ranged from 72.35% to 95.86% with relative standard deviation (RSD) ranging from 1.98% to 8.70% at three spiking levels (0.05 mg/kg, 0.5 mg/kg, 1.0 mg/kg). The method was also successfully applied to the determination of metribuzin and its transformation products in tomato samples collected from an experimental field.