分散固相萃取净化与液相色谱/串联质谱法测定牛奶中8类禁用药物残留

建立了牛奶中8类禁用药物的液相色谱-串联质谱( LC- MS/MS)检测方法.分析物包括5种硝基咪唑、7种β-受体激动剂、9种雄性激素、7种糖皮质激素、3种雌性激素、2种镇静剂、1种氯霉素以及6种二羟基苯甲酸内酯共40种禁用药物.样品以β葡萄糖苷醛酶/芳基硫酸酯酶在乙酸铵缓冲液中酶解,用氨化和酸化乙腈各提取一次.提取液经改良的分散固相萃取(QuEChERS)净化,浓缩后采用C18色谱柱分离(150 mm×2.1 mm i.d.,3.0 um).以甲醇和水(含0.1％甲酸)、乙腈和水分别作为正、负电喷雾离子化模式的色谱分离流动相进行梯度洗脱,多反应监测模式进行定性和定量分析.7种药物以内标法定量；33种药物以基质标准曲线外标法定量,氯霉素在0.02～0.4μg/kg; 39种药物在0.20～ 10.0 μg/kg范围内相关系数(r)均大于0.99;定量限(S/N=10)在0.07～0.93 μg/kg之间.分别以各个药物0.5,1和2倍MRPL( Minimum required performance limits)浓度水平加标验证实验,回收率范围60.3％～119.3％范围；相对标准偏差小于18.9％.

Determination of 8 Species of Banned Drugs in Bovine Milk by Using QuEChERS Cleanup Approach and Liquid Chromatography-Tandem Mass Spectrometry

A method was developed for determination of 8 species of unauthorized drugs in bovine milk by liquid chromatography-tandem mass spectrometry(LC-MS/MS).All target drugs covered 5 nitroimidazoles,7 β-agonists,9 androgens,7 glucocorticoids,3 estrogens,2 sedatives,1 chloramphenicol and 6 resorcylic acid lactones.After homogenization,the sample was mixed with β-glucuronidase/arylsulfatase for enzymatic reaction in ammonia acetate buffer and followed by extraction with basic and then acidic acetonitrile solutions.Cleanup of the extracts was processed by a modified dispersive solid phase extration(QuEChERS).The analystes were then separated by a C18column(150 mm×2.1 mm i.d.,3.0μ) utilising gradient elution with methanol/water(containing 0.1% formic acid) and acetontrile/water,and finally detected by tandem mass spectrometry in positive/negative ESI mode.Identification and quantification were achieved by LC-MS/MS with multi-reaction monitoring.Isotope internal standards for 7 compounds and matrix-matched calibrations were respectively used to quantify the residue contents.Good linearity in response was obtained in the concentration range of 0.02-0.40 μg/kg for chloramphenicol and 0.20-10.0 μg/kg for the other 39 analytes,with correlation coefficients larger than 0.99.The limits of quantification(S/N=10) was around 0.07-0.93 μg/kg.Method validation was carried out at half minimum required performance limits(MRPL),MRPL and double MRPL level of each substance,and the recoveries were in the range of 60.3%-119.3% with relative standard deviations(RSD) smaller than 18.9%.