Determination of deltamethrin residues in plant materials by liquid chromatography/tandem mass spectrometry with electrospray ionization.

This paper describes a selective and sensitive method that uses liquid chromatography/tandem mass spectrometry with positive electrospray ionization (ESI+) for the determination of deltamethrin in a variety of crops. Samples were extracted by conventional high-speed blending. Some samples required no further cleanup; others were cleaned up by gel permeation chromatography, strong cation-exchange cartridges, or partitioning with n-hexane. In the determinative step, the buffered neutral mobile phase, consisting of 10 mM ammonium acetate (pH 6.8) and methanol, and ESI+ provided strong ammonium adduct formation to [M+NH4]+ at m/z 523, and the multiple-reaction monitoring (MRM) transition at m/z 523/281 was used for the quantitation of deltamethrin. A second MRM transition at m/z 525/283 was used for confirmation. The limit of quantitation (LOQ) values were 0.01 mg/kg for edible materials and 0.05 mg/kg for nonedible materials. Mean overall recoveries at the LOQ and the 10-fold LOQ ranged from 73 to 96%, and the relative standard deviations were <10% for all samples materials analyzed.