UPLC-MS/MS法同时测定牛奶中替米考星、地塞米松、氟苯尼考和氯霉素残留

试验旨在建立一种同时测定牛奶中替米考星（tilmicosin）、地塞米松（dexamethasone）、氟苯尼考（florfenicol）和氯霉素（chloramphenicol）的超高效液相色谱-串联质谱（ultra performance liquid chromatography-tandem mass spectrometry，UPLC-MS/MS）法。牛奶样品经乙腈提取后，将提取液通过Oasis PRiME HLB固相萃取小柱净化，净化后的样液经氮吹浓缩后，用样品稀释液溶解并用正己烷进一步除去脂肪获得待分析样品，进行UPLC-MS/MS分析。采用CAPCELL PAK C18 MGⅢ-H色谱柱（2 mm×100 mm，3 μm）进行液相色谱分离，以甲醇（A）-含0.01%甲酸的0.1 mmol/L甲酸铵溶液（B）为流动相进行梯度洗脱：0~1.0 min，90%至60% B；1.0~3.0 min，60%至30% B；3.0~4.4 min，30%至20% B；4.4~4.5 min，20%~90% B；4.5~6.0 min，90% B。在多反应监测（multiple reaction monitoring，MRM）模式下进行质谱测定，以基质匹配标准溶液外标法定量。结果显示，替米考星、地塞米松、氟苯尼考和氯霉素在1.0~100.0 μg/L范围内均具有良好的线性关系（r>0.999）。方法的最低检测限（limits of detection，LODs）为0.1~0.2 μg/kg，定量限（limits of quantity，LOQs）为0.2~0.5 μg/kg，当4种化合物在牛奶中的添加水平为0.5、5.0和25.0 μg/kg时，回收率为78.6%~94.7%，相对标准偏差（relative standard deviations，RSDs）为2.4%~10.1%。本试验建立的UPLC-MS/MS方法简便、灵敏、准确，适用于牛奶中替米考星、地塞米松、氟苯尼考和氯霉素的同时测定。

Simultaneous Determination of Tilmicosin,Dexamethasone, Florfenicol and Chloramphenicol Residues in Milk by UPLC-MS/MS Method

An analytical method was established for the simultaneous determination of tilmicosin,dexamethasone,florfenicol and chloramphenicol in milk by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method.The analytes in milk samples were extracted with acetonitrile,the extract solution was purified by the solid phase extraction cartridge with Oasis PRiME HLB.After concentrated by nitrogen blowing instrument,the analyzed samples were dissolved with sample diluent and excepted fat with n-hexane.The separation was performed on a CAPCELL PAK C18 MG Ⅲ-H column (2 mm×100 mm,3 μm) by gradient elution using methanol(A)-0.1 mmol/L ammonium formate containing 0.01% formic acid (B) as mobile phase:0 to 1.0 min,90% to 60% B;1.0 to 3.0 min,60% to 30% B;3.0 to 4.4 min,30% to 20% B;4.4 to 4.5 min,20% to 90% B;4.5 to 6.0 min,90% B.The analytes were determined by MS/MS under MRM mode,and quantified by matrix-matched external standard method.The results showed that there were good linearities between the peak areas and the concentrations in the range of 1.0 to 100.0 μg/L,with correlation coefficients (r) more than 0.999.The limits of detection (LODs) for the developed method was 0.1 to 0.2 μg/kg,and the limits of quantity (LOQs) was 0.2 to 0.5 μg/kg.Recoveries of 4 compounds ranged from 78.6% to 94.7% when the spiked levels were 0.5,5.0 and 25.0 μg/kg,with the relative standard deviations (RSDs) were 2.4% to 10.1%.Therefore,the developed UPLC-MS/MS method was simple,sensitive and accurate for simultaneous determination of tilmicosin,dexamethasone,florfenicol and chloramphenicol in milk.