称取茶叶样品2.00 g于聚丙烯离心管中，加入水8.00 mL使茶叶浸润展开，加入乙腈10.00 mL，超声提取20 min，加氯化钠1 g和无水硫酸钠4 g，离心5 min，分取乙腈提取液3.00 mL，加入于已预置N-丙基乙二胺（PSA）150 mg和无水氯化钙200 mg的净化管中，混匀后离心5 min使提取液净化。分取此净化液0.50 mL，加入10 mmol·L^-1甲酸铵溶液和6 mmol·L^-1甲酸溶液（以体积比1∶1混合）的混合溶液0.50 mL，混匀后引入ACQUITY UPLC BEH C₁₈色谱柱进行分离，以不同比例的（A）甲酸铵-甲酸混合溶液（浓度及配比见上述描述）和（B）乙腈的混合液为流动相进行梯度洗脱。质谱测定中采用电喷雾离子源正离子（ESI⁺）和多反应监测（MRM）模式。采用基质匹配法制作标准曲线以减小基质效应的影响。在上述条件下，所测定的两种杀虫剂（吡虫啉和噻嗪酮）可达到良好分离和测定。两种杀虫剂的线性范围均在100.0 μg·L^-1以内，其测定下限（10S/N）依次为0.01，0.005 mg·kg^-1。以空白样品为基体，加入被测物的标准溶液进行回收试验，测得回收率均大于（含）80.0%，测定值的相对标准偏差（n=6）均小于13%。应用所提出方法分析了28批次茶叶样品，在4批次样品中检出了吡虫啉，其质量分数为0.012~0.048 mg·kg^-1；在3批次样品中检出了噻嗪酮，其质量分数为0.024~0.63 mg·kg^-1，但均未超过规定的最大残留量0.5 mg·kg^-1和10 mg·kg^-1。

2.00 g of tea sample were moistened with 8.00 mL of water in a polypropylene centrifuging tube and extracted ultrasonically with 10.00 mL of acetonitrile for 20 min. After addition of 1 g of NaCl and 4 g of anhydr. Na₂SO₄, the mixture was centrifuged for 5 min. An aliquot of 3.00 mL of the acetonitrile extract was taken and purified by mixing with 150 mg of PSA and 200 mg of anhydr. CaCl₂ which were placed beforehand in the purification tube, and then the mixture was centrifuged for 5 min. An aliquot of 0.50 mL of the purified extract was taken, and mixed with 0.50 mL of a mixed solution of 10 mmol·L^-1 HCOONH₄ solution and 6 mmol·L^-1 HCOOH solution at a volume ratio of 1:1. The extract was introduced and passed through the ACQUITY UPLC BEH C₁₈ chromatographic column. Mixtures of (A) mixed solution of HCOONH₄-HCOOH (described above for its preparation) and (B) acetonitrile in various ratios were used as mobile phase in the gradient elution. Mode of ESI⁺ and of MRM were adopted in MS/MS determination. The method of matrix matching was used in the preparation of standard curves to overcome the matrix effect. The 2 pesticides, imidaclopride (ICP) and buprofezin (BPFZ) were separated and determined satisfactorily under the above conditions. Linearity ranges for the 2 pesticides were found same within 100.0 μg·L^-1. Values of lower limits of determination (10S/N) found were 0.01 mg·kg^-1 and 0.005 mg·kg^-1 respectively. Recovery was tested by addition of standard solutions to blank sample as matrix, giving results of recovery over (including) 80%. Values of RSDs (n=6) found were all less than 13%. Twenty-eight batches of tea samples were analyzed by the present method, ICP was found in samples of 4 batches of tea with mass fractions ranged from 0.012 mg·kg^-1 to 0.048 mg·kg^-1, and BPFZ was found in samples of 3 batches of tea with mass fractions in the range of 0.024-0.63 mg·kg^-1. These determined values were all lower than the specified max. limits of residual amounts of the pesticides, i.e. 0.5 mg·kg^-1 (for ICP) and 10 mg·kg^-1 (for BPFZ).