液相色谱-串联质谱法测定蜂蜜中双甲脒及其代谢产物残留量

称取蜂蜜样品2.00g,加入同位素内标40ng,用pH7的磷酸二氢钾-磷酸氢二钠缓冲溶液溶解并稀释至10.0mL。充分混匀后,加入乙腈10.0mL和氯化钠2.0g,离心涡旋提取5min。取上层乙腈相保留待用,于下层水相中再加入乙腈10mL重复提取1次。合并两次提取液,加乙腈定容至20.0mL。分取此提取液1.0mL,加入于己预置N-丙基乙二胺(PSA)25mg、十八烷基硅烷(C18)10mg和MgSO430mg的离心管中,充分混匀后,高速离心,进行分散固相萃取(dSPE)净化。转移全部上清液,加水定容至2.0mL,此溶液供液相色谱-串联质谱法(LC-MS/MS)分析。色谱分离中采用XDB-C18色谱柱为固定相,用不同比例的φ0.15%甲酸溶液(A)和乙腈(B)的混合液作为流动相进行梯度淋洗。所得各洗脱液按工作条件进行MS/MS测定双甲脒及其代谢物单甲脒、2,4-二甲基苯基甲酰胺和2,4-二甲基苯胺的残留量。由于采用空白蜂蜜作基体加入混合标准溶液制作工作曲线,并加入同位素内标参与定量,有效地克服了基质效应。上述4种化合物工作曲线的线性范围为0~100μg·kg^-1,测定下限(10S/N)依次为0.10,0.20,5.0,2.0μg·kg^-1。在实际样品基体中加入3个浓度水平的标准溶液(5.0,10,20μg·kg^-1)进行回收试验,测得回收率均大于80%,测定值的相对标准偏差(n=6)均小于10%。所提出方法具有简便、快速的优点,其测定下限能满足目前国内外的规定要求。

Determination of Amitraz and Its Metabolites in Honey by LC-MS/MS

2.00 g of honey sample were taken and 40 ng of the isotopic internal standard were added. The mixture was dissolved and diluted to 10.0 mL with potassium dihydrogen phosphate-sodium hydrogen phasphate buffer solution of pH 7. The solution was extracted twice with acetonitrile (10.0 mL for each extraction and 2.0 g of NaCl were added in the 1st extraction) by centrifuging and swirling for 5 min. The 2 supernatants were combined and its volume was made up to 20.0 mL with acetonitrile. An aliquot of 1.0 mL of the solution was transferred to a centrifuging tube in which 25 mg of PSA, 10 mg of C18 and 30 mg of MgSO4 were added preliminarily, and the mixture was centrifuged at high speed to perform purification by dispersive SPE. Whole of the supernatant was taken and its volume was made up to 2.0 mL with water. This solution was used for LC-MS/MS analysis. In LC separation, XDB-C]8 chromatographic column was used as stationary phase, and mixtures of (A)φ 0.15% formic acid and (B) acetonitrile in various proportions were used as mobile phase in gradient elution. Eluates obtained at various time-intervals were used for MS/MS determination of residual amounts of Amitraz and 让s 3 main metabolites, i. e., N-2, 4-dimethylphenyl-N-methylformamidine, N-(2, 4-dimethylphenyl) formamide and 2, 4- dimethylaniline in the honey sample. In preparation of working standard curves, mixed standard solutions of the 4 analytes were added to a blank honey sample as matrix, and internal standard was used for quantification simultaneously, interference due to matrix effect was effectively overcome. Linearity ranges for the 4 compounds were in the same range of 0-100 μg·kg^-1, with th&r lower limits of determination (10S/N) were found as follows 0.10, 0.20,5.0 2.0 μg·kg^-1. Tests for recovery and precision were performed by addition of standard solutions at 3 concentration levels (5.0, 10 and 20 μg·kg^-1) to a blank honey sample as matrix. Values of recovery found were all greater than 80%, and values of RSD (n = 6) found were all less than 10%. It was shown that the proposed method has specialties of easy and rapid in manipulations, and furthermore, values of lower limits of determination for the 4 analytes were found to meet with the requirements of regulations given by our country or abroad.