地质样品中痕量铑的火试金预富集中子活化分析

Determination of Trace Rhodium in Geological Samples by Fire Assay and Neutron Activation Analysis

简述了铅试金和镍锍试金富集地质样品中痕量铑的分离方法,并结合中子活化分析测量了5种地质标准物质中铑的含量。铅试金法的流程回收率(n=4)为81.5%±1.2%;镍锍试金法的流程回收率(n=6)为75.1%±3.9%,对简单化学标准和地质标准物质基体,铑的回收率相近。对5种地质标准物质中铑含量的分析结果与标准值在不确定度范围内一致。铅试金中子活化法可实现10-9铑含量的准确测量,镍锍试金中子活化法可实现10-10铑含量的准确测量。对两种富集方法中的干扰因素进行了讨论,并对铅的自吸收效应进行了修正。探测极限的计算结果表明:镍锍试金预富集并用平面锗探测器测量,可获得更好的分析灵敏度。

Two pre-concentration methods for rhodium in geological samples, lead fire assay and nickel sulfide fire assay, were briefly described. Using fire assay combined with neutron activation analysis （NAA）, rhodium in 5 certified reference materials were measured. The recoveries of rhodium by lead and nickel sulfide fire assay were 81.5%±1.2% and 75.1%±3.9%, respectively, and the latter was proved to be independent on matrices of chemical standards and geological standard materials. The analytical results of rhodium in 5 geological standard materials are well agreed with the certified values. Rhodium of 10^-9 level was accurately measured by NAA combined with lead fire assay, and 10^-10 level was accurately measured by NAA combined with nickel sulfide fire assay. Interference factors in the two pre-eoneentration methods were discussed, and correction for lead absorption was also carried out. Calculations of the detection limits show that a higher sensitivity is available with a planar germanium detector and a nickel sulfide fire assay.