蔬菜中硝酸盐的快速化学分析

Chemical analysis of nitrate in vegetables

蔬菜是人们日常生活中维生素与矿物质的重要来源,其在生长过程中蓄积的硝酸盐可在储藏、加工过程中被还原成亚硝酸盐,从而产生食品安全性问题,在蔬菜中对其监测具有必要性。依据硝酸和苯酚在浓硫酸介质中发生硝化反应、生成有色物质的原理,利用标准硝酸盐在浓硫酸介质中与苯酚反应,在分光光度计上定量测定其吸光度后绘制出标准曲线,从而对蔬菜中的硝酸盐进行定量分析。通过优化前处理和反应条件,消除了亚硝酸盐、色素、多酚等物质对测定的干扰,无需对样品中的硝酸盐进行转化就可以直接测定,方法简便、快捷、可靠,反应灵敏并且准确度和精确度较高。

Vegetables are important sources of vitamins and minerals in our daily life. Nitrate accumulated during vegetable growth might be reduced into nitrite during its storage and processing. And this might lead to food safety problem. So it is desired to supervise nitrate content in vegetables to insure their safety. In our study we studied the chemical analysis method of nitrate because nitrate could react with phenol in concentrated H2SO4 to form a yellow compound. We employed standard nitrate solutions to react with phenol and determined their absorbances in spectrophotometer. The standard curve obtained thus could be used in determination of nitrate for vegetables. After optimizing the pretreatment and reaction conditions, the interferences of nitrite, polyphenols and pigment existed in samples were all eliminated. The analysis method didn＇t need transforming nitrate into nitrite as ordinary method. It was simple, rapid and trusty with good sensitivity and precision.