ANALYSIS OF PRECIOUS-METAL ALLOYS BY RADIO-FREQUENCY GLOW-DISCHARGE ATOMIC-EMISSION SPECTROMETRY

Analytical figures of merit for trace elements in gold, platinum, silver, and sterling silver alloys have been evaluated using radio frequency glow discharge atomic emission spectrometry (rf-GD-AES). Results presented here illustrate rapid plasma stabilization times (<1 min), short-term precision of <1% RSD, and long-term stability of <5% RSD for major element lines, which are characteristic of the rf-GD plasma. Calibration curves linear over 2-3 orders of magnitude are possible with a general improvement in linearity by ratioing the signal to an internal standard. It is found that the novel use of the signal background as an internal standard is an excellent means for improving analytical accuracy. Similarities in sputtering rates allow the use of multimatrix calibration, emphasizing the fact that there are negligible matrix effects within glow discharge plasmas. Limits of detection on the parts per billion level are recorded for many trace species in the precious metals. The figures of merit reported here indicate that rf-GD-AES is well suited for the precise, accurate, and sensitive analysis of precious metals.