高增敏碘量法掩蔽连测微克量级锰和铬

HIGHLY SENSITIVE IODOMETRIC AMPLIFICATIONMETHOD FOR SIMULTANEOUS DETERMINATION OFMICROGRAM AMOUNTS OF Mn AND Cr

介绍了测定微克量级Ｍｎ（Ⅱ）和Ｃｒ（Ⅲ）的简单、快速、高增敏碘量法。在ｐＨ＝３０的醋酸盐介质中，没有焦磷酸钠存在时，Ｍｎ（Ⅱ）和Ｃｒ（Ⅲ）同时被过量加入的高碘酸根氧化，而有焦磷酸钠存在时，只有Ｍｎ（Ⅱ）被氧化；过剩高碘酸根用钼酸根掩蔽后，加入碘化钾，滴定游离出的单质碘。Ｍｎ（Ⅶ）和Ｃｒ（Ⅵ）混合物及Ｍｎ（Ⅱ），Ｍｎ（Ⅶ），Ｃｒ（Ⅲ）和Ｃｒ（Ⅵ）混合物，可以用亚硫酸钠还原后再以本法测定。相对于常规滴定，本法分别对锰和铬增敏２０和１２倍。此法成功地测定了几种样品。

A simple, rapid and highly sensitive iodometric amplification method was developed for the determination of microgram amount of Mn(Ⅱ)and Cr(Ⅲ). The method is based on both oxidations of Mn(Ⅱ)as well as Cr(Ⅲ) in the absense of sodium pyrophosphate and only oxidation of Mn(Ⅱ) in the presence of sodium pyrophosphate with excess of periodate in acetate buffer(pH=3.0),removal of unreacted periodate by masking with molybdate, and subsequent titration of the liberated iodine after adding iodide.The developed method was found suitable for the analysis of the mixture of Mn(Ⅶ)and Cr(Ⅵ) and the elemental analyses of Mn and Cr in the mixture of Mn(Ⅱ), Mn(Ⅶ), Cr(Ⅲ) and Cr(Ⅵ) after the reduction with sodium sulphite, too. Various samples have been successfully analysed by this method with 20 times and 12 times amplification for Mn and Cr, respectively.