A modified multi-residue method for analysis of 150 pesticide residues in green beans using liquid chromatography-tandem mass spectrometry.

摘要

Three methods of sample preparation were compared for LC-MS/MS analysis of 150 pesticides in green beans. MS parameters were optimized for sensitivity and 2 multiple reaction monitoring modes were used. Samples were extracted in acetonitrile, ethyl acetate or acetone and partitioned in dichloromethane:petroleum ether (3:1). The extracts were dissolved in methanol:buffer (10mM ammonium formate) solution (1:1) at pH 4.0. Stabilities of the tested pesticides in 5 different calibration mixtures (pH 3, 4, 5, 6 and 7) during storage for 2 wk were also determined. All pesticides demonstrated 90-110% recovery at pH 4; however, recovery rates of individual pesticides were pH-dependent, indicating that acidic pH was most suitable for preparation and determination of multi-residue preparations. The optimized LC-MS parameters were evaluated in recovery tests, using samples inoculated with 0.01, 0.05 or 0.1 mg/kg pesticides. All 150 pesticides could be detected at 0.01 mg/kg with acceptable recovery and precision.