Method Validation for Quantitative Analysis of Metribuzin in Wheat by Liquid Chromatography-Tandem Mass Spectrometry

A high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the accurate determination of metribuzin levels in wheat. The widespread use of this herbicide in the production of wheat is of concern and could follow as well as the need for methodology, which required simple sample preparation being needed. Validation of method was done as per single laboratory validation approach. Samples were extracted through a modified quick, cheap, effective, rugged and safe technique. Sample preparation includes extraction by acetonitrile solvent and cleans up by C18, primary secondary amine and anhydrous MgSO4 for dispersive solid-phase extraction. LC-MS/MS was calibrated at 5 calibration levels with high correlation coefficients (r2) >0.995. Limit of detection and limit of quantitation of metribuzin were 0.01 and 0.03 μg/g, respectively. The mean recovery percentages lie in the range of 87-97 with standard deviation for repeatability (RSDa) <10% at three spiking levels (0.03, 0.15 and 0.30 μg/g). Combined uncertainty (U = 0.0017) and expanded uncertainty (2U = 0.0033) were fairly consequential. The method may successfully be applied to other cereals samples for determination of metribuzin.