钒V-次磷酸钠-偶氮胂Ⅲ体系催化动力学光度法测定痕量钒

Catalytic kinetic spectrophotometric determination of trace vanadium with vanadium V-sodium hypophosphite-arsenazo Ⅲ system

基于 0 .0 16mol/L的H2 SO4 介质中 ,痕量钒 对次磷酸钠 (NaH2 PO2 )还原偶氮胂Ⅲ (AsAⅢ )的褪色反应有明显的阻抑作用 ,建立了测定痕量钒 的动力学光度法。钒 质量浓度在 0～ 4 0 μg/L范围内服从比尔定律 ,方法检出限为 0 0 5 8μg/L。在 2 5mL溶液中 ,测定 0 1μg钒 的相对标准偏差为 1 5 % (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 46 80kJ/mol。用于测定人发和茶叶样品中痕量钒 ,相对标准偏差为 3 0 %～ 4 2 % ,标准加入回收率为 98 2 %～ 10 1 4%。

A new kinetic spectrophotometric method for the determination of trace vanadium *% has been developed;the method is based on the inhibitory effect of trace vanadium*% on the reduction of arsenazoⅢ(AsAⅢ) with sodium hypophosphite in 0.016 mol/L sulphuric acid solution.Beer's law is obeyed in the concentration of 0～4.0 μg/L for vanadium*% with the detection limit of 0.058 μg/L.The relative standard deviation for the determination of vanadium*% at the concentration of 0.1 μg/25 mL is calculated to be 1.5%(n=11).The factors such as acidity,concentrations of reactant,reactive time,temperature, influence of coexisting ions on the reaction and the optimum conditions of reaction and some kinetic parameters are determined; the apparent activation energy of the reaction is 46.80 kJ/mol.The method has been applied to the determination of trace vanadium*% in human hair and tea samples with the relative standard deviation of 3.0%～4.2% and the recovery of 98.2%～101.4%.