Using ultra performance liquid chromatography-tandem mass spectrometry to analyze 5 pesticide residues in cowpea

A simple and efficient method based on QuEChERS sample cleanup and ultra performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS) detection was developed to analyze residues of cyantraniliprole, spinetoram, dinotefuran, thiamethoxam and acetamiprid in cowpea simultaneously. The samples were homogenized and extracted with acetonitrile. After QuEChERS cleanup, the retention of target compounds was performed on an Acquity UPLC®BEH C18 column by gradient elution. The qualitative and quantitative analyses of 5 pesticides were operated with electrospray ionization mass spectrometry under positive mode using multiple reaction monitoring(MRM) mode. The results showed that the correlation coefficients of calibration curves were over 0.99 in linear range. The average recoveries of the 5 pesticides at three spiked concentration levels (0.01, 0.1 and 1 mg/kg) varied from 71% to 129% with relative standard deviations (RSDs) of 0.90%-20.8%(n=5). The limits of detection(LOD) and quantitation (LOQ) were 0.084-4.0 μg/kg and 0.80-16.60 μg/kg, respectively. In conclusion, this simple and efficient method met the method validation requirements for the determination of these 5 pesticide residues in cowpea.