Determination of Seventeen Mycotoxins in Chinese Herbal Medicines by Ultra-High Performance Liquid Chromatography-Mass Spectrometry with Isotope Dilution

The sample (2.000 g) was placed in 50 mL centrifuge tube, and 20.0 mL of the mixed solution of acetonitrile-water-formic acid (70+29+1) was aded. The mixture was soaked for 60 min. The mixture was extracted on an oscillating mixer for 30 min and ultrasonically extracted for 30 min. After centrifugation, 2.0 mL of the supernatant was taken and 50 μL of the mixed solution with internal standard of isotope was added, and the mixture was diluted with phosphate buffer solution to 20.0 mL to obtain the sample solution. The sample solution was passed through the immune affinity column at a flow rate of 1-3 mL·min^-1. The immune affinity column was eluted with 5 mL of water, and all effluent was discarded. Then the immune affinity column was eluted with 2 mL of methanol-acetic acid (98+2) solution for 2 times, and all the eluent was collected in the test tube. The eluent was evaporated to near-dryness by N₂-blowing at 50℃, and 0.5 mL of acetonitrile-water (1+9) solution was used to dissolved the residue. After centrifugation, the supernatant was analyzed by ultra-high performance liquid chromatography-tandem mass spectrometry. Stable isotopes ¹³C internal standards were used to correct the loss of sample purification and ionization process and eliminate matrix effect. Linear relationships between the ratios of peak areas of 17 mycotoxins to peak areas of the internal standards and the mass concentration of 17 mycotoxins were found in definite ranges, with detection limits (3S/N) in the range of 0.1-2.0 μg·L^-1. Test for recovery was made by standard addition method on the base of blank Chinece herbal medicine sample, giving results in the range of 84.3%-104%, and RSDs (n=6) ranged from 1.9% to 13%.