六堡茶属于后发酵茶,由于采用高温、高湿渥堆发酵工艺,容易受到黄曲霉毒素B₁污染而影响饮用安全,而目前专门针对六堡茶中黄曲霉毒素B₁检测的报道较少,因此提出了QuEChERS-超高效液相色谱-串联质谱法测定六堡茶中黄曲霉毒素B₁含量的方法。取2.50 g过筛的茶叶样品,用2.0 mL水润湿后,以20 mL含1%(质量分数)甲酸的乙腈溶液提取。振荡、离心后,分取1.0 mL上清液,以250 mg无水硫酸镁、15 mg HC-C₁₈吸附剂、80 mg N-丙基乙二胺净化。振荡、离心后,上清液过0.22 μm有机滤膜,取续滤液进行测定。以0.1%(质量分数)甲酸溶液-乙腈为流动相体系进行梯度洗脱,分离后的黄曲霉毒素B₁经电喷雾离子源正离子模式扫描后,采用多反应监测模式检测,外标法定量。结果显示:黄曲霉毒素B₁标准曲线的线性范围为1.44~14.40 μg·L^-1,检出限(3S/N)为0.03 μg·kg^-1;按照标准加入法对空白样品进行4个浓度水平的加标回收试验,回收率为76.3%~87.3%,测定值的相对标准偏差(n=6)为2.5%~5.9%;方法用于50批六堡茶样品分析,均未检出黄曲霉毒素B₁。

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.