EFFECT OF DISCHARGE CONDITIONS ON THE SPUTTERING AND SPATIAL-DISTRIBUTION OF ATOMS IN A RADIOFREQUENCY GLOW-DISCHARGE ATOMIZER FOR ATOMIC-ABSORPTION SPECTROMETRY

The effects of discharge conditions on the sputtering, spatial distributions and transport patterns of sputtered atoms in a demountable, radiofrequency (r.f.) glow discharge (GD) atomizer, were investigated. Results obtained for sputtering of oxygen-free hard copper indicate that the GD plume is constricted by an increase in the Ar gas pressure and disturbed by Ar gas/vacuum flow. It is shown that the glow is an inhomogeneous medium and that most of the sputtered Cu atoms are localized in the front of the sampling orifice. Independent control of flow rate and pressure of the sputtering gas (Ar) is critical in determining the spatial distribution of analyte atoms within the atomizer chamber. Both the flow rate and the pressure of the Ar gas affect the removal of ground-state atoms from the analysis volume. The plasma location at different discharge parameters was also investigated in this study. The results show that the r.f. GD source is able to sustain a stable plasma which enables the sequential atomic absorption analysis and depth profiling of samples such as metal alloys.