离子交换分离-石墨炉原子吸收光谱法测定高纯铟中的痕量银

银是高纯铟的常检痕量元素,由于银含量低,一般的分析方法难以达到期望的检出限。本研究样品用硝酸溶解,强酸性阳离子交换树脂分离,试液蒸发浓缩后用石墨炉原子吸收光谱法测定高纯铟中痕量银。通过溶样方法、离子交换分离条件和仪器测定条件实验,结果表明,以0.7 mol/L硝酸作为淋洗液进行分离,样品中痕量砷、铝、铁、锡及大量的铟可被分离除去;铜、镉、镁、镍、锌、铅、硅和铊不能与银分离,但对测定无影响。方法线性范围为0～50 pg,相对标准偏差(RSD,n=8)小于10%,银的检出限为0.3 pg,测定下限为0.8ng/g,比文献方法的0.02～1μg/g中最低者低2个数量级,加标回收率为93.3%～110.0%。本方法由于分离了基体铟,避免了铟对银测定的影响,兼之将试液浓缩,有效地降低了检出限,且测定时无需使用基体改进剂,成本低,灵敏度较高,适合于高纯铟中痕量银的分析。

Determination of Trace Silver in High Purity Indium by Graphite Furnace Atomic Absorption Spectrometry after Separation with Ion-Exchange Resin

The element of Ag was determined frequently in high purity indium. Owing to the low content of Ag, the common analytical method is unsuitable to obtain the desired determination limit. The sample of high purity indium was dissolved in HNO₃, and trace Ag was determined by Graphite Furnace Atomic Absorption Spectrometry (GFAAS) after separation from the matrix with cation-exchange resin and the sample solution was evaporated to a small volume. The optimum conditions of dissolving the sample, separation and determination of GFAAS were investigated. The results show that the sample of just 0.2 g was dissolved completely in 3 mL of HNO₃. The In and trace As, Al, Fe, Sn in the sample were separated efficiently by ion-exchange with elution of 0.7 mol/L HNO₃, besides Cu, Cd, Mg, Ni, Zn, Pb, Si and Tl which did not affect the determination of Ag. In the determination step, the quantification limit was reduced effectively and there was no need to use matrix modifiers because the In was separated completely and the sample solution was evaporated to a small volume. The linear range was 0-50 pg,the detection limit was 0.3 pg,and the quantification limit was 0.8 ng/g. The relative standard deviations (RSD, n=8)were less than 10%, and the standard addition recoveries were in the range of 93.3% to 110.0%. The established method has the merits of low cost, easy and quick operation and was qualified for determination of trace Ag in high purity indium.