PRACTICAL ASPECTS IN THE DETERMINATION OF GASEOUS ELEMENTS BY RADIOFREQUENCY GLOW-DISCHARGE ATOMIC-EMISSION SPECTROMETRY

The determination of gaseous elements such as nitrogen and oxygen in s olid samples is complicated by the presence of these elements in the a tmosphere. In the case of glow discharge (GD) based methods, introduct ion of atmospheric gases through vacuum seals or via the discharge gas leads to; overestimation of their concentrations in the solid samples and very high background equivalent concentration (BEG) values, The p ractical considerations necessary for the determination of gaseous ele ments is demonstrated here in the determination of nitrogen in metals with a radiofrequency glow discharge atomic emission spectrometry (rf- GD-AES) source. Meticulous. care in the construction and gas-vacuum pl umbing of the rf-GD-AES source can greatly circumvent these difficulti es, In addition, the use of ultra high purity (99.999%) discharge gase s is shown to be insufficient and further purification by the use of a heated metal (Zr) getter is required, Careful attention to the sample changing protocol also improves system performance, Ultimately, very low background levels of residual gases can be achieved, with concomit ant improvements in sputtering rates and plasma stabilization times. D etection limits for nitrogen determinations in a steel reference mater ial are determined to be of the order of 1-10 ppm, Having made these i mprovements, the data suggest that rf-GD-AES can be used practically f or the bulk and depth-resolved determination of gaseous elements (incl uding N, O, and S) in metals and nonconductive materials.