LC-MS/MS法测定液态奶中苯甲酸

Quantitative determination of benzoic acid in liquid milk with liquid chromatography-tandem mass spectrometry

目的:建立液相色谱-串联质谱法(LC-MS/MS)测定牛奶中苯甲酸的方法。方法:以氘化苯甲酸为内标,牛奶用甲醇直接处理沉淀蛋白后,经液相色谱分离、电喷雾离子化串联质谱进行检测,苯甲酸和内标的多反应监测(MRM)扫描离子通道m/z分别选择为121.0→77.0和126.0→82.0,其色谱保留时间为1.9 min,每个样品分析用时5.0 min。结果:在50 ng/ml～5000 ng/ml范围内,苯甲酸呈现良好的线性关系(r=0.9997)。批内、批间精密度分别为2.5%～3.9%、3.6%～5.6%,加标回收率分别为102.6%～103.1%、99.6%～102.2%。在测定的液态牛奶中,苯甲酸含量从112 ng/ml～5053 ng/ml不等。结论:该方法的样品处理简便快速,检测专一灵敏,可满足牛奶中苯甲酸定量检测的要求。

Objective：To establish a liquid chromatography-tandem mass spectrometric method（LC-MS/MS） for the determination of benzoic acid in commercial milk.Methods：Milk samples were deproteinized with methanol and benzoic acid concentration was determined by LC-MS/MS with negative electrospray ionization using deuterium-labelled internal standard（IS）.Analyte and IS were detected on multiple reaction monitoring（MRM） mode by the transitions from the precursor to the product ion（m/z 121.0/77.0 and m/z 126.0/82.0）.The retention time was 1.9 min and total run time was 5.0 min for each sample.Results：Calibration curve was linear in the range from 50 ng/ml to 5000 ng/ml with a correlation coefficient of 0.9997.The intra and inter-batch precision（RSD） ranged from 2.5%～3.9% and 3.6%～5.6%,and the recoveries were 102.6%～103.1% and 99.6%～102.2%.Among the liquid milk investigated,benzoic acid concentration of 112 ng/ml～5053 ng/ml was observed.Conclusion：The LC-MS/MS method is a simple,sensitive and specific assay for the quantitative determination of benzoic acid in milk.