Determination of 30 organophosphorus pesticides in eight traditional Chinese medicine in Zhejiang (Zhebawei) by liquid chromatography-tandem mass spectrometry

A method for simultaneous determination of 30 organophosphorus pesticides in eight traditional Chinese medicine of Zhejiang (called Zhebawei) was established. Considering the complexity of Chinese herbal medicine and difficulty in purification, nano-ZrO₂ and mesoporous molecular sieve MCM-41 were selected as dispersive solid phase extraction (d-SPE) cleanup adsorbents. The cleanup process was systematically optimized with Rhizoma Corydalis as the representative matrix, and combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. The results showed that using 30 mg nano-ZrO₂ and 50 mg MCM-41 as d-SPE cleanup adsorbents, the linearity for the pesticides was good in the concentration range of 0.001-0.25 mg/L and the correlation coefficient (r) was greater than 0.99, except for cyanofenphos, trichlorphon (0.002-0.25 mg/L) and dichlorvos (0.005-0.25 mg/L). The limit of quantitation (LOQ) was 0.01 mg/kg except for dichlorvos (0.05 mg/kg). Except for fenthion and dichlorvos, the average recoveries of the 28 pesticides in the samples ranged from 64% to 125% at spiking level of 0.05 mg/kg, and the relative standard deviations (RSDs) ranged from 0.05% to 11%. The method is simple, rapid, accurate and reproducible, and has good applicability in the Zhebawei of Zhejiang, which makes up for the lack of detection technology of organophosphorus pesticide residues in the Zhebawei of Zhejiang.