COMPARISON BETWEEN DIRECT-CURRENT AND RADIOFREQUENCY GLOW-DISCHARGE MASS-SPECTROMETRY FOR THE ANALYSIS OF OXIDE-BASED SAMPLES

Glow discharge mass spectrometry (GDMS) using either a direct current (de) or a radiofrequency (rf) discharge has been evaluated. For conducting samples, comparable results are obtained, as indicated by the uniformity in relative sensitivity factors (RSFs). For the analysis of rare earth oxide materials, the RSFs for de GDMS are far less affected by changes in discharge pressure and sample to exit-orifice distance than those obtained for rf GDMS. Despite the higher variability of RSFs for rf GDMS, very stable and reproducible plasma conditions are obtained when working at a fixed pressure and distance. The latter is indicated by the internal (within-sample) and external (sample-to-sample) reproducibility of less than 5 and 15%, respectively.