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    QuEChERS净化-超高效液相色谱-串联质谱法测定茶叶中吡虫啉和噻嗪酮的残留量

    UPLC-MS/MS Determination of Residual Amounts of Imidacloprid and Buprofezin in Tea with Purification by QuEChERS

    • 摘要: 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

       

      Abstract: 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).

       

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