液相色谱-高分辨质谱法在中国东北地区农作物有机硒形态分析中的应用

Determination of Organic Selenium Compounds in Crops by Liquid Chromatography-Quadrupole/Electrostatic Field Orbitrap High-resolution Mass Spectrometry

随着公众对富硒产品的关注,对富硒农作物中硒含量的研究越来越受到人们的重视。针对现有方法测定农作物有机硒的基体效应和多原子离子质谱干扰问题,本研究利用液相色谱与抗干扰能力强的四极杆/静电场轨道阱高分辨质谱相结合,建立了农产品中有机硒的形态分析方法。经优化以超声波辅助蛋白酶XIV提取农作物中有机硒,用Waters Symmetry RP18液相色谱柱分离,以纯水和乙腈作为流动相进行梯度洗脱,采用正、负离子切换同时测定了硒代蛋氨酸、硒代胱氨酸、甲基硒代半胱氨酸。三种有机硒在负离子模式下采用Full MS/dd-MS2扫描模式对目标物进行定性筛查和确证,三种有机硒在5~500μg/L的浓度范围内线性关系良好,相关系数均大于0.997,检出限为1.0~4.7μg/kg,回收率为76.4%~116.0%,相对标准偏差(RSD)≤6.5%。与现有方法比较,本方法线性范围宽,适用于多种谷物和蔬菜类样品的分析。将建立的方法应用于测定中国粮食主产区黑龙江地区多种农作物的可食部分,结果发现谷类中以硒代蛋氨酸为主,蔬菜类以甲基硒代半胱氨酸为主,并且该地区农作物的有机硒含量处于较低水平,亟待强化补硒。

BACKGROUND:As more attention is paid to selenium-rich products,the research on the determination of selenium content in crops has become more and more significant.However,existing methods for determining organic selenium has interferences of the matrix effect and polyatomic ion,which affect the accuracy of the measurement.OBJECTIVES:To establish a rapid method to determine selenium species pf organic selenium in agricultural products by liquid chromatography-quadrupole/electrostatic field orbitrap high-resolution mass spectrometry(LC-Q Exactive Orbitrap MS).METHODS:The selenium species were extracted using an ultrasonic extraction system with a mixture of protease XIV.The separation was carried out on a Waters Symmetry RP18 column by gradient elution with water and acetonitrile as mobile phases.The selenomethionine,selenocystine and methylselenocysteine were simultaneously analyzed in switching positive and negative modes.The quantitative and qualitative analyses were carried out by high-resolution mass spectrometry with electrospray ionization(ESI)source in negative ion acquisition mode under Full MS/dd-MS2 mode.RESULTS:Under the optimal conditions,good linearity was obtained in the respective concentration ranges.The limits of detection for three compounds were in the range of 1.0-4.7μg/kg.The recoveries ranged from 76.4%to 116.0%with relative standard deviations less than 6.5%.CONCLUSIONS:Compared with existing methods,this method has a wider linear range and is suitable for the analysis of a variety of grain and vegetable samples.The established method has been applied to the determination of the edible part of a variety of crops in Heilongjiang,which is the main grain production area in China.The results show that selenomethionine is the main ingredient in cereals,and methylselenocysteine is the main ingredient in vegetables,and that the organic selenium content of crops in this area is at a low level.Therefore,selenium supplementation is urgently needed.