Determination of mycotoxins in pu-erh tea, black tea, and green tea samples

Abstract

To establish a robust method for the determination of mycotoxins in tea samples, and to provide means for the quality and safety control of tea products. Samples of 20 tea products acquired from international market were extracted by organic solvents (acetonitrile containing 0.1% formic acid) or hot water, respectively. The extracts were analyzed by UPLC-MS/MS. A good linear regression was achieved in a range of 39.1 to 5 000 ng·L -1 for aflatoxin B 1 (AFB 1 ) and aflatoxin G 1 (AFG 1 ), 117 to 15 000 ng·L -1 for aflatoxin B 2 (AFB 2 ) and aflatoxin G 2 (AFG 2 ), 2.44 to 313 ng·L -1 for fumonisin B 1 (FB 1 ), fumonisinB 2 (FB 2 ) and fumonisin B 3 (FB 3 ), and 3 125 to 5 000 ng·L -1 for deoxynivalenol, with recovery rates between 85.7% and 99.6%. The coefficient of the linear equation for all standards was greater than 0.999 0, and the RSD value was less than 10%. Mycotoxins were detected in several tea samples using the two extraction methods but with different outcomes. The levels of mycotoxins detected ranging from 0.15 to 7.31 μg·kg -1 were well below the State or US FDA regulation limits of mycotoxins in food products. Both methods are simple, accurate, and sensitive, and thus, suitable for the quantitative determination of mycotoxins in different food products. The method with the 80℃ hot-water extraction is more appropriate to determine the trace amounts of mycotoxins in tea leaves that are likely to be present in brewed tea liquor, while organic solvent method is more suitable for the detection of mycotoxins in ingestible foods.