亲水作用色谱-电喷雾串联质谱法检测原料奶及奶制品中的三聚氰胺

建立了亲水作用色谱-电喷雾串联质谱测定原料奶及奶制品中三聚氰胺的方法。样品采用1%三氯乙酸水溶液-乙腈（体积比为1∶1）混合溶液提取，混合型阳离子交换反相固相萃取柱（MCX）富集净化，亲水作用色谱柱分离，电喷雾串联四极杆质谱仪进行检测。结果表明，三聚氰胺的质量浓度在0.05～10.0 mg/L范围内具有良好的线性关系。原料奶及奶制品中的三聚氰胺在0.5，2.5和10 mg/kg 3个添加水平下，平均回收率为76.3%～98.7%，相对标准偏差均小于6.8%；定量限（S/N＞10）为0.05 mg/kg。

Determination of melamine residue in raw milk and dairy products using hydrophilic interaction chromatography-electrospray ionization tandem mass spectrometry

A method for the determination of melamine residue in raw milk and dairy products was developed using hydrophilic interaction chromatography-electrospray ionization tandem mass spectrometry (HILIC-ESI-MS/MS). The melamine residue in the test sample was extracted with 1% trichloroacetic acid-acetonitrile (1∶1， v/v) solution. The homogenate was centrifuged and the supernatant was collected. The extract was cleaned up using a mixed-mode cation exchange (MCX) solid-phase extraction cartridge and then concentrated, and analyzed by HILIC-ESI-MS/MS. The gradient chromatographic separation was performed using a hydrophilic silica column (250mm×4.6 mm, 5 μm) with 10 mmol/L ammonium acetate buffer (pH 3.0) and acetonitrile as the mobile phases. Due to its hydrophilic property, melamine was well retained on the column and seperated from other compounds. It effectively reduced matrix effect. A triple quadruple mass spectrometer equipped with an electrospray ionization source was employed for the qualitative and quantitative measurement of melamine. The melamine was quantified using the fragments produced from the protonated melamine ion through multiple reaction monitoring (MRM) in positive ion mode. Two MRM transitions from the protonated melamine ion (m/z 127→85 and m/z 127→68) were monitored. The average recoveries were between 76.3% and 98.7% in the spiked range of 0.5 to 10 mg/kg in raw milk and dairy products, and the relative standard deviations were less than 6.8%. The linear range was from 0.05 to 10.0 mg/L. The limit of quantification （S/N＞10） was 0.05 mg/kg. The method is highly selective and sensitive for the measurements of melamine and adequate for the analysis of melamine in raw milk and dairy products.