基于新型微腔体微波反应器的微波辅助衍生-气相色谱质谱法快速测定水果中的有机酸

Rapid determination of organic acids in fruits by gas chromatography-mass spectrometry following microwave-assisted derivatization based on the novel microcavity microwave reactor

设计制作了一种新型微腔体微波衍生反应器,采用红外成像技术研究了反应器中样品的温度分布和升温特征。结果表明,设计的微波衍生反应器具有优于传统谐振腔微波反应器的体积小巧、操作简单、样品升温匀速平稳、温度分布均匀、易于控制等特点。据此建立了微波辅助衍生-气相色谱质谱法(microwave-assisted derivatization-gas chromatography mass spectrometry,MAD-GC-MS)快速测定有机酸的方法,采用GC-MS鉴定出琥珀酸和柠檬酸衍生产物分别为琥珀酸二甲酯和柠檬酸三甲酯,获得最佳衍生条件:衍生剂硫酸体积分数20%,用量1.0 mL、微波功率30 W、微波衍生时间4 min。相对于传统衍生方法,衍生时间从120 min大幅度缩短至4 min,且衍生效率明显提高。该方法对琥珀酸和柠檬酸的检出限分别为0.019 mg/mL和0.026 mg/mL,使用该方法测定了柠檬、猕猴桃和番木瓜中琥珀酸和柠檬酸含量,回收率为98.34%~102.52%,标准偏差为1.63%~3.25%。该研究所设计的微腔体微波反应器适于色谱分析前对有机酸等成分进行精确、平稳可控地快速微波衍生处理,在食品分析领域具有良好的应用前景。

A novel microcavity microwave reactor was designed and prepared,and the temperature distribution and temperature rising characteristic of the samples in the reactor were investigated by infrared imaging technology.The microwave derivatization reactor was superior to the traditional resonant cavity microwave reactor in the characteristics of smart shape,easy to use,stable temperature rise,uniform sample temperature distribution and easy to control.The method for the rapid determination of organic acids by microwave-assisted derivatization-gas chromatography mass spectrometry(MAD-GC-MS)was established.Two derivatives for citric acid and succinic acid were identified as dimethyl succinate and trimethyl citrate by GC-MS,respectively.The optimal derivatization conditions were obtained as follows:the volume fraction of sulfuric acid in derivatizing agent was 20%;derivatizing agent dosage was 1.0 mL;microwave power was 30 W and microwave derivatization time was 4 min.Compared with the traditional heating method,the derivatization time was greatly reduced from 120 min to 4 min,and the derivative efficiency was significantly improved.The limits of detection(LODs)for succinic acid and citric acid were 0.019 mg/mL and 0.026 mg/mL,respectively.The contents of succinic acid and citric acid in lemon,kiwi fruit and papaya were determined by this method with the recovery in the range of 98.34%-102.52%and the standard deviation(RSD)in the range of 1.63%-3.25%.The microcavity microwave reactor designed in this paper is suitable for accurate,stable and controllable rapid microwave derivatization of organic acids before chromatographic analysis,it has a great application prospect in food analysis.