The direct determination of trace metals in gold and silver materials by laser ablation inductively coupled plasma mass spectrometry without matrix matched standards

Abstract

Typically, accurate trace element determination in solid samples by laser ablation ICP-MS requires calibration with matrix matched standards. Trace metal analysis was performed in high purity gold, high purity silver and 14 karat gold-silver alloys. A Nd : YAG laser was used to evaporate solid samples of precious metals into an inductively coupled plasma mass spectrometer. Analytical data and a study of the crater sizes indicated that approximately the same amount of material for both gold and silver samples was vaporized by a Nd : YAG laser operated in a Q-switched mode with the following parameters: 210 mJ laser energy; 8 Hz repetition rate; and focused 7 mm below the sample surface. High purity gold and silver, and a 14 karat gold-silver alloy were analyzed for trace metals common to gold and silver reference materials. In general, the determination of Fe, Ni, Cu, Zn, Pd, Pt, Pb, and Bi did not strongly depend on whether gold or silver reference materials were used for calibration. This permits these trace metals to be determined directly with only one set of reference materials, by laser ablation ICP-MS, in a wide variety of gold-silver alloys.