Aflatoxin B₁ and sterigmatocystin: method development and occurrence in tea

Tea is one of the most popular beverage in the world and may be contaminated by fungi and mycotoxins during processing. To analyse aflatoxin B₁ (AFB₁) and sterigmatocystin (STC) in three types of tea, a simple, fast, sensitive and reliable method of these two myxotoxins was developed. Recoveries obtained ranged from 95.9% to 118.0% and the RSDs were between 0.3% and 11.2%. The range of LODs was 0.2-0.45 µg/kg for AFB₁ and 0.04-0.12 µg/kg for STC. The range of LOQs was 0.67-1.73 µg/kg for AFB₁ and 0.13-0.40 µg/kg for STC. The optimised procedure was applied to analyse 126 tea samples randomly collected from different markets in China. AFB₁ was not detected, but STC was determined in 17 samples with concentrations ranging from 0.13 to 4.48 µg/kg. The detection rate of STC was 5%, 8.9% and 33.3% in black tea, green tea and Oolong tea, respectively.