Determination of Residues of 35 Prohibited Pesticides in Typhonii Rhizoma by Gas Chromatography-Tandem Mass Spectrometry with QuEChERS

On the basis of the addition of the fifth method in the fourth part general rule 2341 of Pharmacopoeia of the People's Republic of China (2020 edition), the title method was proposed, and conditions of the pre-treatment, chromatography and mass spectrometry were optimized to solve the problems of easy conversion and decomposition of isomeric pesticides in the detection process. The 35 prohibited pesticides were extracted from the sample using acetonitrile and QuEChERS extraction kit. Impurities were removed using dedicated agricultural residue purification tube. The resulting sample extract was concentrated by nitrogen blowing and diluted with acetonitrile, and then mixed with triphenyl phosphate internal standard solution. The sample solution obtained was analyzed by GC-MS/MS. Prohibited pesticides in the sample solution were separated by DB-17MS capillary column under programmed temperature conditions, detected by triple quadrupole mass spectrometer equipped with EI source in MRM mode, and quantified by matrix matching method combined with internal standard method. It was shown that linear relationships between values of the mass concentration ratio and the peak area ratio of each prohibited pesticide to internal standard were kept in definite ranges, with correlation coefficients not less than 0.999 8 and detection limits (3S/N) ranging from 0.16 μg·kg^-1 to 5.00 μg·kg^-1. Test for recovery was made by standard addition method, giving results in the range of 61.1%-121%. RSDs of the determined values for each pesticide obtained from tests of the instrument, method and intermediate precision were in the ranges of 1.2%-1.8% (n=6), 2.3%-5.5% (n=6) and 2.5%-5.7% (n=12), respectively. The proposed method was applied to the analysis of actual samples, and the 35 prohibited pesticides were not detected in 6 batches of Typhonii Rhizoma samples.