高效液相色谱-串联质谱法测定牛(羊)奶中阿莫西林的残留

Determination of amoxicillin residues in milk by high performance liquid chromatography-tandem mass spectrometry

【目的】建立奶中阿莫西林残留检测的高效液相色谱-串联质谱方法．【方法】2g样品经乙醇沉淀蛋白质后，转入梨形瓶中旋转蒸发浓缩至约0.5 mL左右，用pH 4.5乙酸铵溶液定容，净化后检测．流动相为乙腈和体积分数0.1％甲酸水溶液，梯度洗脱，经Luna 5μm C18色谱柱分离，采用电喷雾电离，多反应监测正离子模式对阿莫西林进行定量分析．【结果和结论】采用基质匹配法对奶中阿莫西林的含量进行标准校正，在阿莫西林质量浓度为1～400μg· L-1范围内呈现良好的线性关系，相关系数＞0.999；奶中加标样品的检出限（按信噪比 S/N≥3计）为1μg· kg-1，定量限（按信噪比S/N≥10计）为2μg· kg-1．在定量限、1/2最高残留限量（5μg· kg -1）、最高残留限量（10μg· kg-1）、2倍最高残留限量（20μg· kg-1）添加水平下，奶中阿莫西林的平均回收率为75.6％～91.0％，相对标准偏差为1.6％～10.2％．

Objective] An analytical method was developed for the determination of amoxicillin residues in milk by high performance liquid chromatography-tandem mass spectrometry （ HPLC-MS/MS） .[Meth-od] A two-gram milk sample was deproteinized by ethanol .The supernatant was transferred into a pear-shaped bottle to be evaporated to about 0.5 mL,and the residue was dissolved with ammonium acetate so-lution.The sample was determined by HPLC-MS/MS after the purification.The chromatographic separa-tion was achieved on a Luna 5μm C18 column using 0.1%formic acid in water and acetonitrile as mobile phases with gradient elution .The identification of amoxicillin was carried out by MS/MS equipped with electrospray ionization in positive scanning and multiple reaction monitoring （MRM） modes.[Result and conclusion] Matrix-matched calibration standard was used for the quantification .The calibration curve showed perfect linearity in the range of 1-400μg· L-1 , with the correlation coefficient being more than 0.999.The limit of detection （LOD,S/N≥3） was 1 μg· kg-1 in milk,and the limit of quantification （ LOQ,S/N≥10） was 2μg· kg-1 .The mean recoveries varied from 75.6%to 91.0%at the four spiked levels of LOQ,1/2MRL （the maximum residue limit：5μg· kg-1 ）, MRL（10 μg· kg -1 ）,and 2MRL（20μg· kg-1 ） with the relative standard deviations of 1.6%-10.2%.