鸡冠花红褪色速差动力学光度法同时测定铬(Ⅵ)和锰(Ⅶ)

Simultaneous determination of chromium(Ⅵ) and manganese(Ⅶ) by differential reaction rate kinetic fading spectrophotometry of amanranth

研究了铬（Ⅵ）和锰（Ⅶ）氧化鸡冠花红（C20H11N2Na3O10S3）的褪色反应。在硫酸介质中，70℃水浴加热条件下，铬（Ⅵ）和锰（Ⅶ）都能氧化鸡冠花红褪色，但褪色反应速率不同，而且二者无明显的协同效应，据此建立了速差褪色动力学光度法同时测定铬（Ⅵ）和锰（Ⅶ）的新方法。考察了介质的酸度，鸡冠花红的用量，反应温度和时间对褪色反应的影响。选择了最佳实验条件，建立了比例方程，铬（Ⅵ）和锰（Ⅶ）的测定范围分别为0-9.0μg／mL和0-8.0μg／mL，且在该线性范围内铬（Ⅵ）和锰（Ⅶ）的加和性良好。方法应用于工业废水和合金钢标准样品中铬（Ⅵ）和锰（Ⅶ）的同时测定，水样的测定结果与国家标准方法结果相一致，合金钢样品的测定结果同认定值相符。

The fading reaction of chromium（Ⅵ） and manganese（Ⅶ） with oxidation amanranth was studied. In sulfuric acid medium and in water bath at 70℃, chromium（Ⅵ） and manganese（Ⅶ） could both oxidize amanranth with different reaction rate. Moreover, there was no obvious synergistic effect between them. Based on this, a new method to determine chromium（Ⅵ） and manganese（Ⅶ） by differential reaction rate kinetic fading spectrophotometry was established. The effect of medium acidity, the dosage of amanranth, reaction temperature and time on fading were investigated. Under the optimal experi-mental conditions, the ratio equation was established. The determination range of chromium（Ⅵ） and manganese（Ⅶ） was 0-9.0μg/mL and 0-8.0μg/mL, respectively. In this linear range, the additive property of chromium（Ⅵ） and manganese（Ⅶ） was good. This method could be used to determine chromium（Ⅵ） and manganese（Ⅶ） in industrial waste water and standard alloy steel samples simultaneously. The results were in accordant with those measured by national standard methods for water and the results of alloy steel samples were match for the certified values.