Application of electrothermal atomic absorption spectrometry to the determination of trace amounts of indium in metallic zinc and lead

Abstract

Trace amounts of indium in metallic zinc and lead have been determined by graphite furnace atomic absorption spectrometry. The detection limits for three operated furnace systems were evaluated: for SP9-01 (1), 6.0 × 10^–13 g; for HGA-500 (2), 7.0 × 10^–13 g; and for GRM-1268 (3), 1.1 × 10^–11 g, each using 20 µl of sample. Linear calibration graphs were obtained between 0.01 and 0.1 p.p.m. (1), 0.05 and 0.6 p.p.m. (2) and 0.05 and 0.2 p.p.m. (3). Ion-exchange separation employing Xylenol Orange modified Amberlyst A-26 anion exchanger was used as the preliminary step for the determination of indium in Zn-In and Pb-In alloys as interferences from other metals were observed in the indium absorbance. In order to compare the results, two other separation methods for the lead matrix and several different graphite furnace atomisers were used. Molar excesses of Ni, Co, Fe, Cu and Zn of less than 1000 and between a 100 and 1000 molar excess of Al cause a decrease in the indium absorbance. With molar ratios greater than 1000, the suppression caused by Al, Co and Zn disappears and that of Fe becomes less pronounced. Ga causes an enhancement of the indium atomic absorption signal. Equivalent amounts of As, Sb, Bi do not interfere.