EBT-1,2-丙二醇光度法测定食品中微量镁研究

Determination of Trace Magnesium in Foodstuffs by Spectrophotometry with EBT-1,2-propanediol

建立了EBT-1,2-丙二醇水溶液光度法准确测定食品中镁含量的新方法。试样用HNO3-HClO4湿消化,并用钨酸钠消除Ca2+、三乙醇胺-四乙烯五胺混合掩蔽剂掩蔽Te3+、Al3+等干扰离子后,在pH10.5的氨性缓冲溶液中,Mg2+与EBT生成可溶于水的酒红色络合物,在分光光度计波长为520nm处测定其吸光度。测定结果的相对标准偏差小于1.0%,加标回收率在95.4%～102.4%之间。结果表明,改进后的方法操作简便、测定快捷、准确度高、干扰小,测定结果与国家标准方法相符,相对偏差小于2.0%。

A new spectrophotometric method for determining magnesium content in foodstuffs with EBT- 1,2-propanediol as color reagent was developed. After being digested with HNO3-HClO4, samples were added with sodium tungstate to eliminate interference of Ca2＋ and added with triethanolamine-tetlaethylenepentamine to mask Al3＋ and Fe3＋ etc. In ammonia buffer solution at pH 10.5, Mg2＋ and EBT form a claret-red complex, which can be dissolved in water and has a maximum absorbance at 520 nm wavelength. The method is successfully applied for determination of magnesium in different foodstuffs with relative standard deviations of less than 1.0%, relative deviation of less than 2.0% and recoveries of spiked standard of 95.4%-102.4%. The results are consistent with those by China national standard method. The improved method is easily operated with the characteristics of fast determination, high accuracy and little disturbance.