超高效液相色谱-串联质谱法测定牛奶和奶粉中残留的左旋咪唑

建立了一种专属、灵敏的超高效液相色谱-串联质谱(UPLC-MS/MS)测定牛奶和奶粉中左旋咪唑残留量的方法。在碱性环境下用乙酸乙酯超声波提取试样中的左旋咪唑,再经稀盐酸反提取、强阳离子交换(SCX)固相萃取柱净化,采用BEHC18超高效液相色谱柱、乙腈-0.1%甲酸(体积比为15∶85)流动相分离,以电喷雾离子源正离子检测方式进行质谱分析。实验结果表明,在2.0～100.0 μg/L浓度范围内左旋咪唑呈良好的线性关系,其相关系数r=0.997。在低、中、高3个浓度添加水平下,左旋咪唑的回收率为64.5%～102.0%,相对标准偏差小于13.1%。牛奶中左旋咪唑检出限为0.4 μg/kg,奶粉中左旋咪唑检出限为2.0 μg/kg。

Determination of levamisole residue in milk and milk powder by ultra performance liquid chromatography-tandem mass spectrometry

A sensitive and selective method is presented for the determination of levamisole residues in milk and milk powder by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Levamisole in the test samples was extracted with ethyl acetate under alkaline condition, then transferred into dilute hydrochloric acid, and cleaned-up with a strong cation exchange (SCX) column to obtain an extract suitable for the analysis by UPLC-MS/MS. Levamisole was separated by a BEHC18 UPLC column and acetonitrile-1.0% formic acid (15∶85, v/v) as mobile phase, and electrospray ionization was applied and operated in the positive ion mode. The calibration curve was good linear between the peak area and the mass concentration of levamisole from 2.0 to 100.0 μg/L with the correlation coefficient of 0.997. The average recoveries of levamisole spiked in milk and milk powder samples at the three concentrations ranged from 64.5% to 102.0% with the relative standard deviations less than 13.1%. The detection limits of levamisole were 0.4 μg/kg in milk and 2 μg/kg in milk powder.