高效液相色谱-电感耦合等离子体质谱法分析研究西兰花中硒形态

Selenium Speciation in Broccoli by High Performance Liquid Chromatography-Inductively Coupled Plasma-Mass Spectrometry

硒是一种典型的“双功能”元素,摄入不足或摄入过量均会对人体健康产生不利影响,硒的生物活性不仅取决于硒含量,还与硒的化学形态密切相关,因此对食品中不同硒形态进行分析研究具有重要的意义。本文采用高效液相色谱-电感耦合等离子体质谱(HPLC-ICP/MS)联用技术分析研究了市售西兰花中硒酸根[Se(Ⅵ)]、亚硒酸根[Se(Ⅳ)]、硒代胱氨酸(SeCys_(2))、甲基硒代半胱氨酸(MeSeCys)、硒代蛋氨酸(SeMet)。以蛋白酶XIV和Tris-HCl缓冲溶液超声提取西兰花中硒形态,采用C18反相色谱柱为分析柱,10mmol/L柠檬酸和5mmol/L己烷磺酸钠(pH=4.0,含1%甲醇)为流动相,等度洗脱,8min内可实现硒形态的有效分离测定,方法线性范围为0.3~100.0μg/L,线性相关系数(r)均大于0.999,Se(Ⅵ)、Se(Ⅳ)、MeSeCys、SeMet的检出限在1.2~6.0μg/kg(以Se计)范围内。对西兰花样品进行低、中、高三个浓度水平的加标回收试验,加标回收率为81.9%~105.3%,相对标准偏差(RSD)均小于5%。采用本方法分析欧盟有证标准物质——小麦粉(ERM®BC210a)中SeMet的测定值在其标准值范围内。实验结果表明建立的硒形态分析方法适用于西兰花中Se(Ⅵ)、Se(Ⅳ)、MeSeCys、SeMet的测定。检出的11个不同地区市售西兰花样品中硒形态主要为MeSeCys,含量在0.004~0.043mg/kg(以Se计)之间。对方法研究过程中发现的SeCys_(2)稳定性差和不同类型西兰花中Se(Ⅳ)加标回收率差异较大的问题进行分析探讨,通过改变蛋白酶XIV的用量考察了SeCys_(2)的稳定性,结合对西兰花样品基质的分析研究,发现SeCys_(2)稳定性与蛋白酶XIV含量和西兰花基质有关;根据对3种不同类型的西兰花样品中Se(Ⅳ)加标回收试验结果及相关文献报道,推测样品中存在的大量酚类物质会影响Se(Ⅳ)的分析测定。

BACKGROUND:Selenium is an essential trace element and a typical bifunctional element that can affect human health if consumed in insufficient or excessive amounts.The biological activity of selenium depends not only on its intake level but also on its chemical speciation.Selenium comes in various speciation and is divided mainly into inorganic and organic selenium.Inorganic selenium includes selenate[Se(Ⅵ)]and selenite[Se(Ⅳ)],and organic selenium mainly includes selenocysteine(SeCys_(2)),selenomethionine(SeMet),and methylselenocysteine(MeSeCys).It has been found that organic selenium has high bioactivity and bioavailability.At present,while the nutritional effects of selenium are drawing more and more attention,it is very important to analyze and study the different speciation of selenium in food.Since the analysis of selenium speciation is closely related to the sample matrix,the extraction efficiency and stability of different selenium speciation are also related to many factors.At present,the analysis method of selenium speciation in food is still in the research stage.Broccoli is rich in nutrients,such as protein,flavonoids,polyphenols,and vitamins,and is widely loved by people because it contains many kinds of thioglucosides and has a strong ability to gather selenium,which has antioxidant and anti-cancer medical values.Therefore,the analysis and study of selenium speciation in broccoli is of some significance.