Determination of aflatoxins in medicinal herbs by high-performance liquid chromatography-tandem mass spectrometry.

We report a rapid and accurate method to determine the natural occurrence of aflatoxins (AFs) B1, B2, G1 and G2 in medicinal herbs and the analysis of 174 commercial samples by this method. The aim of the present work is to examine the occurrence of the aflatoxins B1, B2, G1 and G2 in common medicinal herbs. The AFs were extracted, purified by immunoaffinity column and analysed by high-performance liquid chromatography-tandem quadrupole mass spectrometry with electrospray ionisation (HPLC-MS/MS). The AFs can be separated within 6 min using an Agilent XDB C₁₈-column. The target analyte AFB1 could be detected at 0.14 µg/kg. A good linear relationship was found for AFG1 and AFB1 in 1-100 pg and AFG2 and AFB2 in 0.8-30 pg (r > 0.9995). The analyte recovery under three different spiking levels was 64-100% with the relative standard deviations (RSD) below 8.19%. This simple and accurate method effectively eliminates false positive detection and can be used to determine the AFs in medicinal herbs to control product quality. We found that in the 174 samples tested, 27 were contaminated with AFs. The incidences of AFB1, AFB2, AFG1 and AFG2 in the samples tested were 15.52%, 14.37%, 6.32% and 2.30%, respectively. We proposed 10 µg/kg total AFs and 5 µg/kg AFB1 as the reasonable maximum limits (ML) in medicinal herbs, and there are 10 samples (5.71% occurrence) in our test that exceeded this proposed limit.