乙基罗丹明B指示反应动力学光度法测定痕量铱

Kinetic Spectrophotometric Determination Trace of lridium(Ⅳ) Based on the Catalytic Reaction of Ethylrhodamine B with Potassium Periodate

提出了动力学光度法测定铱。在磷酸 -氯化钠介质中 ,Ir( )催化高碘酸钾氧化乙基罗丹明 B( ERB)形成褪色化合物 ,适宜条件为 c Na Cl=0 .0 2 mol/ L ,c H3PO4 =0 .1 0 mol/ L ,c KIO4 =2 .0× 1 0 - 3mol/ L ,c ERB=1 .7× 1 0 - 5mol/ L ,I=0 .0 2 ,90℃。铱浓度在 0 .4～ 32μg/L范围校正曲线成直线 ,检出限为 4.0× 1 0 - 10 g/ m L,对 2 0 μg/ L铱测定 1 1次的 RSD为1 .55% ,体系至少稳定 8h。考察了 30多种共存离子的影响。本法满意地用于某些冶金产品和矿石中铱的测定。铱催化反应对 Ir( )、ERB、KIO4 和 H3PO4 均为一级反应 ,表观活化能为 75.82 k J/ mol。

A catalytic spectrophotometric method for the determination trace of iridium is proposed. The method is based on the catalytic action of iridium(Ⅳ) on the oxidation of ethylrhodamine B(ERB) by potassium periodate to form a colorless compound in the phosphoric acid sodium chloride medium.The optimum experimental conditions are c NaCl =0.02 mol/L, c H 3PO 4 =0.10 mol/L, c KIO 4 =0.0020 mol/L, c ERB =1.75×10 -5 mol/L and 90℃. The calibration graphs were linear in the range of 0.4～32 μg/L(Ir). The detection limit is 4.0×10 -10 g/mL. The relative standard deviations for 11 replicate determination of 20 μg/L of iridium(Ⅳ) is 1.55%. The system is stable at least 8 h. Many common ions, 100 fold excess of Au(Ⅲ) and Pd(Ⅱ), and 40 fold excess of Pt(Ⅳ) and Ag(Ⅰ) did not interference with the Ir determination. The method was successfully applied to the determination of trace amounts of iridium(Ⅳ) in some metallurgical products and ores. It was established that iridium catalyzed reaction was first order in Ir(Ⅳ), ERB,KIO 4 and H 3PO 4,respectively. The apparent activation energy for the iridium catalyzed reaction was calculated to be 75.82 kJ·mol -1 .