Simultaneous determination of 35 ultra-trace level organophosphorus pesticide residues in Sanjie Zhentong capsules of traditional Chinese medicine using ultra high performance liquid chromatography with tandem mass spectrometry.

The aim of this study was to develop an analytical method for the simultaneous determination of ultra-trace levels of 35 organophosphorus pesticide residues in Sanjie Zhentong capsules, a traditional Chinese medicine prescription. A method based on multiclass and multiresidue sample preparation was developed. First, samples were hydrated with water at 4°C. A ratio of 1:3 sample/water was used for each of the sample amounts. Then, different extraction solvents were screened. This step was followed by a dispersive solid-phase extraction clean-up procedure using both primary secondary amine and polyamide. A comprehensive sensitive multiresidue liquid chromatography tandem mass spectrometry method was investigated and validated. Good linearity was achieved in the range of 10-500 μg/kg for each analyte. The average recovery ranged from 70 to 120%, except for methamidophos, fonophos, diazinon, and chlorpyriphos-ethyl, the recoveries of which ranged from 60-70% at the lower concentration level. The precision values were lower than 10% for all the compounds in three concentration levels. The limits of detection and limits of quantification values were 0.01-2.1 and 0.05-3.4 μg/kg, respectively. The matrix effects were determined, and most of the compounds showed signal suppression. Finally, this optimized procedure was applied for the analysis of real samples.