Determination of Trace Silver in Geochemical Samples by Inductively Coupled Plasma-Mass Spectrometry with Phosphoric Acid Precipitation Separation

Abstract

BACKGROUND Standard mode with interference correction or kinetic energy discrimination mode is commonly used for the determination of trace silver in geochemical samples by inductively coupled plasma-mass spectrometry (ICP-MS). Interference of both stable isotopes of silver occurs in the mass spectrum of the oxides or hydroxides of zirconium and niobium. Moreover, for samples with a higher content of interfering elements and a lower content of silver, the determination accuracy is low, requiring separation of the interfering element from silver in the solution. OBJECTIVES To develop a method for the determination of trace Ag in geochemical samples. METHODS Common sample digestion methods and chemical separation (ion exchange separation) were introduced in detail and were discussed in this paper. RESULTS As proved by first grade standard materials, the result was consistent with standard recommended values, with the relative standard deviation of 4.3%-12.1% (n=12). The detection limit (3SD) of the method was 0.0072μg/g. CONCLUSIONS This method is suitable for the determination of trace silver in soil, stream sediment and rock samples. The introduction of phosphoric acid does not affect the determination of other conventional elements, and the same digestion solution can be used to determine Ag and other elements.

Keywords

• trace silver
• inductively coupled plasma-mass spectrometry
• geochemical samples
• phosphate precipitation