Glow Discharge Mass Spectrometry for Cobalt Alloys Analysis

A comparison of results obtained using argon/glow discharge mass spectrometry (Ar/GD-MS) and fundamental parameter/X-ray fluorescence analysis (FP/XRF) was made by analyzing of cobalt (Co) alloys. The relative sensitivity factors (RSF) used for GD-MS quantitative analysis were determined using six commercial Co alloy standard reference materials. The analysis objects comprised 16 elements contained in Co alloys: C, Al, Si, P, S, Ti, Cr, Mn, Fe, Ni, Cu, Nb, Mo, Sn, La, and W. A glow-discharge cell for disk samples was used. A sample mask made from Ta, a part of the anode, was employed; it had an internal diameter of 12 mm. The discharge parameters were 1 kV and 3 mA. Samples were put on a liquid sample CLIP with an adherent 6.3-mu m-thick polypropylene film and subjected to a FP/XRF measurement. The sensitivity coefficients (K(ij)) of XRF for Co alloys were determined through measuring identical standard substances, such as GD-MS, and processing thereof using UQ5 software. A commercial Co alloy, Haynes 188, was subjected to chemical analysis; the GD-MS, chemical analysis, and FP/XRF results were compared. The FP/XRF results of the main components (Cr, Fe, Ni, and W) agreed well with the GD-MS and chemical analysis results. The analytical accuracy was satisfactory as 0.18% (Cr) similar to 0.46% (W) in RSD. However, some overestimation occurred for minor, elements such as Cu and La, at low concentrations, where RSD was 10 similar to 17%. On the other hand, the GD-MS results agreed well with results of chemical analysis obtained from P and S at the trace impurity level, minor components, to main components. The analytical accuracy of GD-MS was shown to be within 2% as RSD for most elements, from main components, such as Cr (RSD : 1.2%), Ni (1.0%), and W (0.89%), to elements of trace impurity level, like S (4.5%), including minor components.