UPLC-MS-MS检测饮料中的4-甲基咪唑及其同分异构体2-甲基咪唑

Determination of 4-(5-)-Methylimidazole and Its Isomer 2-Methylimidazole in Beverage by Ultra Performance Liquid Chromatography Tandem Mass Spectrometry

建立超高效液相色谱-串联质谱（ultra performance liquid chromatography-tandem mass spectrometry,UPLC-MS-MS）法检测饮料中的4-甲基咪唑（4-（5-）-methylimidazole,4-Mel）及2-甲基咪唑（2-methylimidazole,2-Mel）的方法.以水溶解样品,OASIS（R）MCX固相萃取柱富集净化后,进入UPLC-MS-MS检测,内标法定量.在优化的条件下,以ACQUITY UPLC（R）HILIC色谱柱（2.1 mm×100mm,1.7 μm）为分析柱,乙腈和5 mmol/L甲酸铵溶液为流动相,在电喷雾正离子多反应监测模式进行检测.结果表明,4-Mel和2-Mel在9～500 ng/mL范围内线性关系良好.方法的定量限为3.0 μg/kg.在4个加标水平下,3种不同基质饮料中4-Mel和2-Mel的平均回收率分别为97.3％和93.7％,相对标准偏差分别为3.8％和3.4％,该方法适用于饮料中4-Mel和2-Mel的检测.利用该方法对市售饮料中4-Mel和2-Mel的含量进行检测,在软饮料、焦糖色饮料及咖啡饮料中检出含有4-Mel或2-Mel;而功能性饮料中未检出4-Mel和2-Mel.

An ultra performance liquid chromatography-tandem mass spectrometry （UPLC-MS-MS） method was developed for the determination of 4-（5-）-methylimidazole （4-Mel） and its isomer,2-methylimidazole （2-Mel）,in beverage.Samples were diluted with water.An OASIS（R） MCX solid phase extraction column was used to purify and concentrate the target analytes.Under the optimal conditions,the analytes were separated by a Waters ACQUITY UPLC（R） HILIC column （2.1 × 100 mm,1.7 μm） using a mobile phase consisting of acetonitrile and 5 mmol/L ammonium acetate aqueous solution.The analytes were detected in multiple-reaction monitoring （MRM） mode via positive electrospray ionization （ESI＋）.The results showed that the calibration curves of 4-Mel and 2-Mel were of good linearity in the range of 9-500 ng/mL.The limit of quantification of the method was 3.0 μg/kg.The average recovery was 97.3％ and 93.7％ at four spiked levels （3.0,25,50 and 75 μg/kg） for 4-Mel and 2-Mel,respectively,and the relative standard deviation （RSD） was 3.8％ and 3.4％,respectively.These figures of merit indicated that the developed method can be used for the determination of 4-Mel and 2-Mel in beverage samples.This method was applied to different beverages.4-Mel or 2-Mel was found in soft drink,caramel colored beverage and coffee.Contrarily,neither of them was found in energy drinks.