A comparison of X-ray fluorescence spectrometric (XRF) techniques for the determination of metal traces,especially in plastics

A comparative study of energy-dispersive X-ray fluorescence techniques (without and with polarized radiation) and a wavelength-dispersive technique was carried out in order to investigate their sensitivity for the quantitative determination of 3d transition metal traces in plastic materials. For this purpose, liquid calibration samples in paraffin oil for the elements Cr, Mn, Co, Ni and Cu were prepared. Calibration lines in the concentration range of 1–100 g/g were evaluated for commercially available XRF-instruments and the results were critically compared. Limits of detection (LOD) ranged from 0.1 to 0.7 g/g for wavelength-dispersive XRF and energy-dispersive XRF with polarized radiation. The LOD's for energy-dispersive XRF without polarized radiation ranged from 0.9 to 8.6 g/g for elements in the same atomic number range between 24 and 29. The application of these optimized methods to the quantitation of wear and corrosion phenomena in plastic extruders and in a relevant model test apparatus, the annular slit tribometer, is elucidated.