氧化偶氮胂Ⅲ褪色光度法测定痕量钴

Kinetic Spectriphotometric Determination of Trace Cobalt Based on Discoloring of ArsenazoⅢ Oxidized by Potassium Dichromate

基于0．02mol／L HCl介质中，痕量钴(Ⅱ)对重铬酸钾氧化偶氮胂Ⅲ褪色反应的催化作用，建立了测定痕量钴(Ⅱ)的动力学光度法。钴(Ⅱ)质量在0～4．0μg/L范围内服从比尔定律，方法检出限为0．076μg/L，在25mL溶液中，测定0．1μg钴(Ⅱ)的相对标准偏差为3．8％(n=11)。讨论了酸度、反应物浓度、温度、反应时间、干扰离子等因素的影响。研究了反应的最佳条件，并测定了一些动力学参数。催化反应的表观活化能为40．73kJ／mol。此法可用于井水、蜂蜜和维生素B12中钴(Ⅱ)的测定，相对标准偏差为1．8％-5．7％，标准加入回收率为99．6％～104．2％。

Based on the catalytic effect of trace cobalt on discoloring reaction of arsenazoⅢ with potassium dichromate in 0.02mol/L hydrochloric acid solution, a method for the determination of trace cobalt by kinetic spectrophotometry has been developed. Beer law is obeyed in the concentration of 0~4.0 μg/L for cobalt with the detection limit is 0.076 μg/L. The relative standard deviation for the determination of cobalt at the concentration of 0\^1 μg/25 mL is calculated as 3.8%(n=11). The factors such as acidity, concentrations of reactant, reactive time,temperature,interference ions of influence on the reaction and the optimum reaction conditions and some kinetic parameters are studied; the results obtained from the studied on the kinetic parameters suggested that the apparent activation energy of the reaction is 40.73 kJ/mol.The method has been successfully applied to the determination of trace cobalt in well water, honey and vitaminB_(12) samples with the relative standard deviation of 1.8%~5.7% and the recovery of 99.6%~104.2%。