重铬酸钾氧化偶氮胂Ⅲ褪色催化光度法测定痕量钴的研究

Spectrophotometric Determination of Trace Cobalt with a Kinetic Procedure Based on the Colour Fading of Arsenazo Ⅲ Oxidized by Potassium Bichromate

在醋酸－醋酸钠缓冲介质中痕量钴（Ｉ）对重铬酸钾氧化偶氮胂ＩＩ褪色反应有显著的催化作用，催化反应的表观活化能为２５．６２ｋＪ·ｍｏｌ－１．据此建立了测定痕量钴的催化动力学分析法．线性范围为０～３５０ｎｇ·ｍＬ－１，检出限为２．０ｎｇ·ｍＬ－１（Ｃｏ）．除Ｆｅ（Ｉ）外，其余常见共存离子基本不影响钴的测定．本法重现性较好，用于测定人发、茶叶、土壤和废水中钴的含量，结果满意．

A kinetic method for the determination of trace cobalt was established based on its catalytic effect on the colour fading reaction of arsenazo Ⅲ oxidized by potassium dichromate. The optimized conditions for determination were:pH4.5, [K 2Cr 2O 7]=2.0×10 -4 mol·L -1 , [Arsenazo III]=2.6×10 -5 mol·L -1 , 80℃. The calibration graph is linear for 0～350 ng·mL -1 ,and the detection limit is 2.0 ng·mL -1 (Co). The active energy of catalytic reaction is 25.62 kJ·mol -1 . Most foreign ions do not interfere with determination of cobalt except for Fe(II). The cobalt contents in hair, tea, soil and water samples had been determined, the results were satisfactory.