高碘酸钾-孔雀石绿催化动力学光度法测定痕量铱(Ⅳ)

Determination of trace iridium (Ⅳ) by catalytic kinetic spectrophotometry with potassium periodate-malachite green

在稀硫酸介质中及加热95℃的实验条件下,痕量Ir(Ⅳ)对高碘酸钾氧化孔雀石绿的褪色反应具有显著的催化作用,据此建立了催化动力学光度法测定痕量Ir(Ⅳ)的新方法。研究了最佳实验条件,测定了动力学参数。在所选实验条件下,非催化反应(吸光度A0)与催化反应(吸光度A)的吸光度差值ΔA在618nm处与Ir(Ⅳ)在0～0.06μg/mL范围内呈良好的线性关系,检出限为1.3×10-10g/mL。该催化反应为准一级反应,表观速率常数为1.850×10-4/s,表观活化能为48.03kJ/mol。方法用于分子筛催化剂和活性炭中痕量铱(Ⅳ)的测定,其回收率小于103%,相对标准偏差为2.2%和1.9%。

Iridium （Ⅳ） can catalyze the fading reaction of potassium periodate with malachite green at 95 ℃ in diluted sulfuric acid medium. Based on this phenomenon, a catalytic kinetic spectrophotometric method for the rapid determination of iridium（Ⅳ） was established. Optimum experimental conditions were discussed and kinetic parameters were determined. Under selected experimental conditions, the absorbence difference AA between non-catalytic reaction system （A0） and catalytic reaction system （A） at 618 nm remained good linear relationship with iridium（IV） concentration in the range of 0-0.06 μg/mL and the detection limit was 1.3× 10^-10 g/mL. This catalytic reaction was pseudo first order re- action, whose apparent ratio constancy was 1. 850× 10^-4/s and apparent activated energy was 48.03 kJ/mol. The method was applied to the determination of trace iridium （Ⅳ） in molecular sieves and active carbon with the recovery below 103 % and relative standard deviation of 2.2 % and 1.9 %, respectively.