茶叶样品(10 g)加水20 mL浸泡10 min后,加乙腈50 mL,超声提取5 min,加氯化钠5 g,振荡,静置分层;取有机相,吹氮至近干,加入丙酮-正己烷(3+7)混合液2 mL溶解残渣。所得溶液经Florisil固相萃取柱净化后进行色谱分离。用BEH C18色谱柱作固定相,以不同体积比的甲醇和0.1%(φ)甲酸溶液的混合液作流动相进行梯度洗脱。质谱分析中采用电喷雾正离子和多反应监测模式。外标法定量,基体匹配制作标准曲线。结果表明:印楝素A和B的质量分数均在2.50~50.0 μg·kg-1范围内与相应的峰面积呈线性关系,检出限(3S/N)分别为2.5,5.0 μg·kg-1。在3个浓度水平上用标准加入法做回收试验,测得回收率为81.6%~95.1%,相对标准偏差(n=6)为1.1%~3.9%。应用此法分析了3种茶叶样品,其中单枞茶中印楝素的残留量最高。

The tea sample (10 g) was soaked in 20 mL of water for 10 min, and then extracted ultrasonically with 50 mL of acetonitrile for 5 min. The extract was shaked with 5 g of NaCl and let to stand for phase separation. The organic phase was taken and evaporated to near dryness by N2-blowing. The residue was taken up with 2 mL of a mixture of acetone and n-hexane (3+7). The solution obtained was purified on Florisil SPE column and then separated by UHPLC using BEH C18 column as stationary phase and mixtures of methanol and 0.1% (φ) formic acid solution, mixed in various volumic ratios, as mobile phase in gradient elution. In MS analysis, ESI+ and MRM mode were adopted. Quantification was attained by external standard method with preparation of standard curves by matrix-matching method. Linear relationships between values of peak area and mass fraction of azadirachtin A and azadirachtin B were obtained in the same range of 2.50-50.0 μg·kg-1 with detection limits (3S/N) of 2.5, 5.0 μg·kg-1 respectively. Tests for recovery were made by standard addition method at 3 concentration levels, giving values of recovery in the range of 81.6%-95.1%, with values of RSD′s (n=6) ranged from 1.1% to 3.9%. The proposed method was used in the analysis of 3 different kinds of tea. It was found that among the 3 tea samples, highest amount of residual azadirachtin was given by the Dancong tea.