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.