催化极谱法测定痕量铑(Ⅲ)
Catalytic Polarographic Determination of Trace Amount of Rhodium(Ⅲ)
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摘要: 铑(Ⅲ)与新试剂2-(5-碘-2-吡啶偶氮)-5-二甲氨基苯胺(5-I-PADMA)在1 mol·L-1乙酸盐缓冲溶液(pH 4.8)中生成稳定的配合物,该配合物在3 mol·L-1高氯酸底液中于-1.01 V(vs.SCE)处产生一灵敏的极谱催化波,据此提出了催化极谱法测定痕量铑(Ⅲ)的方法。铑(Ⅲ)的质量浓度在40.0~400 ng·L-1范围内与一阶导数峰电流呈线性关系,检出限(3s/k)为14.2 ng·L-1。试验结果表明:该极谱波为催化氢波,其电极过程为不可逆过程,电子转移数为1。方法用于铑炭催化剂和标准物质GBW 07198中痕量铑的测定,回收率分别为100%,101%;测定值的相对标准偏差(n=6)分别为0.70%,1.8%。Abstract: A stable complex between rhodium and the new reagent, 2-(5-iodo-2-pyridylazo)-5-dimethylaminoaniline (5-I-PADMA) was formed in 1 mol·L-1 acetate buffer solution of pH 4.8, and a sensitive catalytic polarographic wave of this complex was observed at the potential of -1.01 V (vs.SCE) in 3 mol·L-1 HClO4 medium. Based on this fact, a method of catalytic polarography for the determination of trace amount of Rh(Ⅲ) was proposed. Linear relationship was kept between values of 1st derivative of peak current and mass concentration of Rh(Ⅲ) in the range of 40.0-400 ng·L-1 with detection limit (3s/k) of 14.2 ng·L-1. It was found that the polarographic wave was a catalytic hydrogen wave, and the electrode process was an irreversible reduction process, with number of electron transfer of 1. The proposed method was used in the analysis of samples of Rh-C catalyst and a CRM of GBW 07198, giving values of recovery and RSD (n=6) of 100% and 0.70% for the sample of Rh-C catalyst, and 101% and 1.8% for the CRM of GBW 07198.