Integrated Parallel Beam WDS/EDS Analysis: Benefits and Limitations for Geoscience Research

The performance of an integrated parallel beam wavelength-dispersive/energy-dispersive microanalysis system mounted on a field emission scanning electron microscope has been compared with that of a conventional electron microprobe, using the same reference samples and as close as possible operational conditions. Tests on standards of known composition reveal internally consistent results for the former, and no obvious advantage of wavelength-dispersive over energy-dispersive spectroscopy has emerged for major elements without peak overlaps. Rather, because an energy-dispersive spectrometer can acquire all energies of the X-ray spectrum concurrently, conveying a lower electron dose per atom, it has the advantage of being faster and milder to minerals. In all cases, however, element migration may be significant, especially for monovalent, large ionic radius elements such as K and Na.