离子色谱-质谱联用法测定鲜榨果汁中α-羟基酸

Determination ofα-Hydroxy Acid in Fresh Juice by Ion Chromatography-mass Spectrometry

建立了离子色谱-质谱联用法测定果汁中6种α-羟基酸的检测方法。样品经去离子水提取,选用AS11-HC质谱专用柱进行分离,以0.8 mmol/L KOH溶液作为初始浓度进行梯度洗脱,经过色谱分离后,采用电喷雾电离源负离子模式(ESI;),选择离子监测模式(SIM)进行测定,电导检测器定量,质谱定性。结果表明,6种α-羟基酸在0.005~5mg/L范围内线性关系良好,相关系数大于0.99,苹果酸、酒石酸和柠檬酸检出限为0.002 mg/L,乙醇酸检出限为0.015 mg/L,乳酸检出限为0.005 mg/L,扁桃酸检出限为0.025 mg/L。运用该方法测定了12种水果中α-羟基酸,结果表明:12种水果中未检出扁桃酸和乙醇酸,山楂、柠檬、脐橙、菠萝、猕猴桃、甜瓜属于柠檬酸型水果;红心和白心火龙果、油桃、苹果、西瓜属于苹果酸型水果;葡萄为酒石酸型水果。该方法具有操作简单、灵敏度高等特点,可满足果汁中α-羟基酸的测定要求。

A method for determination of 6α-hydroxy acids in fresh juice by Ion Chromatographymass Spectrometry(IC-MS)was established.The samples were extracted with deionized water.The extract was separated by AS11-HC column.Gradient elution was carried out with 0.8 mmol/L KOH solution as initial concentration.After separation by chromatography,electrospray ionization source negative ion mode(ESI;)was selected,and ion monitoring mode(SIM)was used for determination.Conductance detector was quantified and mass spectrometry was identified.The analytical results showed that the calibration curves for 6α-hydroxy acids were linear in the range of 0.005-5 mg/L by IC-MS,with the correlation coefficients higher than 0.99.The detection limits of malic acid,tartaric acid and citric acid were 0.002 mg/L,the quantitative limits of glycolic acid,lactic acid and mandelic acid were 0.015 mg/L,0.005 mg/L and 0.025 mg/L respectively.The method was used to determine the content ofα-hydroxy acid in 12 fresh fruit,which showed that:mandelic acid and glycolic acid were not detected in 12 fresh juices;Hawthorn,lemon,navel orange,pineapple,kiwi fruit and melon were citric acid fruits;red dragon fruit and white dragon fruit,nectarine,apple and watermelon were malic acid fruits;and the grape was tartaric acid.This method has advantages of time saving,convenience and sensitivity,and can meet the requirements of determination ofα-hydroxyl acids in fruit juice.