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基于以H3PO4为反应介质,用HAc-NaAc(1+8)(pH5.7)作缓冲溶液,在沸水浴中加热条件下,痕量铱(Ⅳ)能灵敏地催化高碘酸钾氧化甲基绿的褪色反应,建立了一种测定痕量铱(Ⅳ)的新催化光度法。研究了反应的最佳条件。催化反应吸光度A与非催化反应吸光度A0的差值ΔA与铱(Ⅳ)的质量浓度ρ在0～2.0μg/25mL范围内呈良好的线性关系。检出限为2.97×10-10g/mL。对1μg/25mL铱(Ⅳ)测定的相对标准偏差为1.7%(n=11)。测定了动力学参数。该催化反应对铱(Ⅳ)为一级反应,总反应为准一级反应。反应的表观速率常数为4.613×10-4/s,表观活化能为40.56kJ/mol。该方法用于分子筛样品和活性炭中痕量铱(Ⅳ)的测定,回收率97.9%～104.4%。
Based on the reaction of H3PO4 with HAc-NaAc (1 + 8) (pH5.7) as a buffer solution, trace amount of iridium (Ⅳ) can catalyze the oxidation of methyl iodide by potassium periodate under the condition of heating in boiling water bath Green fading reaction, a new catalytic spectrophotometry was established for the determination of trace amounts of iridium (Ⅳ). The optimum reaction conditions were studied. The difference ΔA between the absorbance A of the catalytic reaction and the absorbency A0 of the non-catalytic reaction and the mass concentration ρ of the iridium (Ⅳ) showed a good linear relationship in the range of 0-2.0 μg / 25 mL. The detection limit was 2.97 × 10-10g / mL. The relative standard deviation of 1 μg / 25 mL iridium (IV) assay was 1.7% (n = 11). Kinetic parameters were determined. The catalytic reaction of iridium (Ⅳ) for the first reaction, the total reaction quasi-first-order reaction. The apparent rate constant of the reaction is 4.613 × 10-4 / s, and the apparent activation energy is 40.56kJ / mol. The method was applied to the determination of trace amounts of iridium (Ⅳ) in molecular sieve samples and activated carbon with the recoveries of 97.9% -104.4%.