Determination of Deltamethrin Residues in Plant Materials by Liquid Chromatography/Tandem Mass Spectrometry with Electrospray Ionization

Abstract

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.

Quantification of Nonpersistent Pesticides in Small Volumes of Human Breast Milk with Ultrahigh Performance Liquid Chromatography Coupled to Tandem Mass Spectrometry

“…A possible contributing factor to the lack of sensitivity may be the form of the molecular ion, as pyrethroids were better detected with mass spectrometry as ammonium adducts . Although acidified ammonium formate was part of the mobile phase in this study, ammonium adduct formation was reported by others to improve when the mobile phase was buffered to pH 6.8 . Instrument and column performance may also change over time and affect sensitivity, suggesting that LOD and corresponding LOQ estimations should be measured at the time of each analysis.…”

“…43 Although acidified ammonium formate was part of the mobile phase in this study, ammonium adduct formation was reported by others to improve when the mobile phase was buffered to pH 6.8. 44 Instrument and column performance may also change over time and affect sensitivity, suggesting that LOD and corresponding LOQ estimations should be measured at the time of each analysis. Measuring the LOD during each run may allow harmonization across batches.…”

Transmission-mode direct analysis in real time and desorption electrospray ionization mass spectrometry of insecticide-treated bednets for malaria control

“…5 Previous LC-ESI-MS studies of pyrethroids, including deltamethrin and permethrin, demonstrated that the primary ESI pathway was cation adduction. 26,27 In particular, ammonium adducts were reported to dominate the LC-MS spectra, and only a minimal amount of protonated species was observed. A number of TM-DESI solvents (e.g., methanol, acetonitrile, water-methanol solutions) were tested in the present study.…”

Quantification of non-persistent pesticides in small volumes of human breast milk with ultra-high performance liquid chromatography coupled to tandem mass-spectrometry

“…43 Although acidified ammonium formate was part of the mobile phase in this study, ammonium adduct formation was reported by others to improve when the mobile phase was buffered to pH 6.8. 44 Instrument and column performance may also change over time and affect sensitivity, suggesting that LOD and corresponding LOQ estimations should be measured at the time of each analysis. Measuring the LOD and LOQ during each run may allow harmonization across batches.…”