LAUSR

In this study, 170 tea samples were investigated for the occurrence of 9,10-anthraquinone (AQ), which was collected from Shandong Province of China in 2018. The contamination levels of AQ were detected by a combination of QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) procedure with gas chromatography tandem mass spectrometry. Under the optimal conditions, the linear range for AQ was from 10 to 200 ng/mL. The recoveries ranged from 95.6% to 101%, with the coefficient of variation less than 3.99%. The limits of detection and quantification for AQ were 0.001 and 0.003 mg/kg, respectively. Owing to the good accuracy, precision, and high sensitivity, the proposed method is suitable for the determination of trace AQ in tea. The results demonstrated that AQ was detected in 67.1% of tea samples, with the average concentration of 0.0160 mg/kg. The contamination levels varied from tea types and sale locations. The individual average values of AQ in green tea, black tea, oolong tea, and pu-erh tea products were 0.0161 mg/kg, 0.0140 mg/kg, < 0.003 mg/kg and 0.0337 mg/kg, respectively. The level of AQ contamination in a descending order was wholesale markets, supermarkets, specialty stores, and production bases. In addition, the influence of different tea-producing areas on AQ contamination level in Shandong Province was investigated. Contamination levels of AQ did not show significant correlation with the producing areas in Shandong. Although a high incidence of AQ contamination was detected in tea samples, the total average value meets the maximum limit of the European Union (0.02 mg/kg).