Evaluation of matrix effect in determination of mevinphos stereoisomers in tobacco by supercritical fluid chromatography tandem mass spectrometry

Supercritical fluid chromatography tandem mass spectrometry (SFC-MS/MS) is an important tool for the analysis of stereoisomer in complex matrices. Matrix effect is a critical factor that can significantly compromise the accuracy of pesticide residue analyses by mass spectrometry. The influence of matrix effect in the stereoselective analysis of mevinphos in tobacco by SFC-MS/MS was studied. Experiments have been performed to compare the response of mevinphos isomers in standard solutions prepared in acetonitrile with their responses in tobacco extracts. The presence and extent of matrix effects are simultaneously affected by several factors (matrix concentration, matrix type, matrix dilution, and chromatographic separation conditions). In this study, a QuEChERS method coupled with a dilution strategy eliminated most of the matrix effects. The mean recoveries for all isomers were 85.2%-99.3%, with 2.2%-7.7% intra-day relative standard deviations (RSDs) and 3.6%-6.9% inter-day RSDs at 0.05, 0.2 and 1.0 mg/kg levels. Good coefficients of determination (R-2 >= 0.9995) were achieved for all studied isomers over the concentration range of 25-500 ng/mL.