Determination of Aflatoxin B₁ in Liupao Tea by Ultra-High Performance Liquid Chromatography-Tandem Mass Spectrometry with QuEChERS

Liupao tea belongs to post fermented tea. Due to the high temperature and high humidity pile fermentation process, it is easy to be polluted by aflatoxin B₁, which affects the drinking safety. However, there are few reports on the detection methods for aflatoxin B₁ in Liupao tea, so a method for the determination of aflatoxin B₁ in Liupao tea by ultra-high performance liquid chromatography-tandem mass spectrometry with QuEChERS was proposed. The sifted tea sample (2.50 g) was taken, and extracted with 20 mL of acetonitrile solution containing 1% (mass fraction) formic acid after wetting with 2.0 mL of water. After oscillation and centrifugation, 1.0 mL of the supernatant was purified with 250 mg of anhydrous magnesium sulfate, 15 mg of HC-C₁₈ adsorbent and 80 mg of N-propyl ethylenediamine. After oscillation and centrifugation, the supernatant was passed through 0.22 μm organic filter membrane, and the subsequent filtrate was taken for determination. The mobile phase system composed of 0.1% (mass fraction) formic acid solution and acetonitrile was used for gradient elution, and aflatoxin B₁ separated was scanned by electrospray ion source with positive ion mode, detected by multi-reaction monitoring mode, and quantified by external standard method. As shown by the results, the linear range of standard curve for aflatoxin B₁ was 1.44-14.40 μg·L^-1, with detection limit (3S/N) of 0.03 μg·kg^-1. Test for recovery was made on the blank sample by standard addition method at 4 concentration levels, giving results in the range of 76.3%-87.3%, and RSDs (n=6) of the determined values ranged from 2.5% to 5.9%. The method was applied to the analysis of 50 batches of Liupao tea samples, and aflatoxin B₁ was not detected.