二苯碳酰二肼光度法测定铬(Ⅵ):不足及改进

Determination of Chromium (Ⅵ) by Diphenylcarbohydrazide Spectrophotometry: Disadvantages and Improvement

有毒重金属铬(Ⅵ)的测定是环境、化学等专业重要的实验内容,教材常用的测定方法是国标二苯碳酰二肼分光光度法(GB7467—1987)。国标方法存在使用挥发性有毒溶剂、操作繁琐等不足,对环境和分析人员不利。对国标方法进行改进,结果证明:可以用乙醇代替有毒的丙酮配制二苯碳酰胺二肼显色剂,用盐酸代替硫酸和磷酸的混合酸,并将盐酸直接加入显色剂中,分析时可一次加入,既简化了操作步骤,提高了工作效率,又减少了显色剂用量,有利于环境和人员健康。将改进的方法应用于废水中六价铬的测定,并与原子吸收光谱法进行比较,结果无显著性差异,能够确保水样中六价铬测定的精密度和准确度。

The determination of toxic heavy metal chromium (Ⅵ) is an important experiment content in the majors of environment, chemistry and etc. As national standard method, the 1,5- diphenylcarbohydrazide spectrophotometry (GB/T 7467-1987) is usually used. However, this national method has some disadvantages of using volatile toxic solvent, cumbersome operation and unfriendliness to the environment and operator. In the improved method, the diphenylcarbohydrazide chromogenic agent was prepared by using ethanol instead of toxic acetone as the solvent. Moreover. hydrochloric acid was instead of the mixed acid of sulphuric acid and phosphoric acid, which was then directly added to the chromogenic agent. This improved method simplified the operation step, improved work efficiency and reduced environmental and health damage.To evaluate accuracy of the proposed method,the concentration of chromium (Ⅵ) in wastewater samples was simultaneously determined by the atomic absorption spectroscopy method. The results showed that there was no significant difference between the two methods.