超高效液相色谱-串联电喷雾四极杆质谱法同时测定牛奶中12种糖皮质激素的残留

采用超高效液相色谱-串联电喷雾四极杆质谱(负离子模式)在多反应监测(MRM)模式下测定了牛奶中12种糖皮质激素的残留。试样中加入pH 5.20的醋酸盐缓冲溶液和甲醇,超声提取，以去除部分蛋白质，然后用正己烷脱脂，依次经HLB柱、硅胶柱和氨基柱等固相萃取柱浓缩和净化后,通过Waters ACQUITY UPLCTM BEH C18色谱柱分离,以甲醇和含0.1%甲酸的水为流动相进行梯度洗脱。在超高效液相色谱-质谱分析过程中以保留时间和离子对(母离子和两个碎片离子)信息比较进行定性,以母离子和响应值高的碎片离子进行定量。该法的检出限为0.02～0.38 μg/kg,最低定量限为0.07～1.27 μg/kg。添加水平为2 μg/kg和0.4 μg/kg时,12种糖皮质激素的加标回收率为69.3%～94.3%,相对标准偏差为3.5%～16.7%。

Simultaneous Determination of Twelve Glucocorticoids Residues in Milk by Ultra Performance Liquid Chromatography-Electrospray Tandem Mass Spectrometry

A comprehensive analytical method based on ultra performance liquid chromatography-electrospray tandem mass spectrometry (UPLC-MS/MS) with negative mode has been developed for the simultaneous determination of twelve glucocorticoids residues in milk. The multi-reaction monitoring mode was employed for the determination. Milk samples were extracted by sonication in a methanol/acetate buffer (pH 5.20) solution, and then defatted with n-hexane. Sample concentration and purification were performed using Oasis HLB, Sep-pak silica and Sep-pak amino-propyl solid phase extraction cartridges. The separation was performed on a Waters ACQUITY UPLC BEH C18 column (100 mm x 1.0 mm i. d., 1.7 microm) with gradient elution using methanol and water (containing 0.1% formic acid) at a flow rate of 0.1 mL/min. Identification of the glucocorticoids was done using retention times and the distribution of diagnostic ion pairs. Quantification of the glucocorticoids was based on the peak areas of the parent ion and a fragment ion with a higher signal. The limits of detection (LOD) of the method were from 0.02 to 0.38 microg/kg and the limits of quantification (LOQ) ranged from 0.07 to 1.27 microg/kg. Average recoveries for the twelve glucocorticoids (spiked at the levels of 2 and 0.4 microg/kg) ranged from 69.3% to 94.3%, with relative standard deviations between 3.5% and 16.7%. Routine tests showed that the method is fast, sensitive and specific for the determination of glucocorticoids residues in milk.