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

Analytical figures of merit for trace elements in gold, platinum, silv er, and sterling silver alloys have been evaluated using radio frequen cy glow discharge atomic emission spectrometry (rf-GD-AES). Results pr esented here illustrate rapid plasma stabilization times (<1 min), sho rt-term precision of <1% RSD, and long-term stability of <5% RSD for m ajor element lines, which are characteristic of the rf-GD plasma. Cali bration curves linear over 2-3 orders of magnitude are possible with a general improvement in linearity by ratioing the signal to an interna l standard. It is found that the novel use of the signal background as an internal standard is an excellent means for improving analytical a ccuracy. Similarities in sputtering rates allow the use of multimatrix calibration, emphasizing the fact that there are negligible matrix ef fects 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 preci ous metals.