Simultaneous determination of aflatoxin B1, B2, G1, G2, ochratoxin A, and sterigmatocystin in traditional Chinese medicines by LC–MS–MS

In this paper we describe a rapid, simple, and cost-effective liquid chromatography–tandem mass spectrometric (LC–MS–MS) method for simultaneous analysis of aflatoxin B1, B2, G1, and G2, ochratoxin A, and sterigmatocystin in 25 traditional Chinese medicines (TCMs). The method is based on single extraction with 84:16 (v/v) acetonitrile–water then analysis of the diluted crude extract without further clean-up. Chromatographic separation was achieved on a C18 column, with a mobile phase gradient prepared from aqueous 4 mmol L−1 ammonium acetate–0.1 % formic acid and methanol. Quantification of the analytes was by selective reaction monitoring (SRM) on a triple-quadrupole mass spectrometer in positive-ionization mode. Special focus was on investigating and reducing matrix effects to improve accuracy. The established method was validated by determination of linearity (r > 0.995), sensitivity (limits of quantification 1.6–25.0 ng L−1), apparent recovery (84.8–110.6 %), extraction recovery (83.6–106.1 %), and precision (relative standard deviation ≤9.9 %) for two representative TCMs, Semen Armeniacae Amarae and Radix Pseudostellariae. The applicability of the method to TCMs other than these was further investigated, and 23 other TCMs with acceptable matrix effects (80.2–118.6 %) were screened. The validated method was finally used to assess mycotoxin contamination of 244 samples of 25 TCMs collected from local hospitals and TCM pharmacies. Aflatoxin B1 and ochratoxin A were detected in 5.3 % of the samples. Sterigmatocystin, the most prevalent mycotoxin contaminant, was present in 26.2 % of the samples tested; this has not been reported previously. The results of this work imply greater attention should be devoted to evaluation of the potential hazard caused by sterigmatocystin in TCMs.