Wavelength-dispersive X-ray fluorescence (WD-XRF) allows measurement of up to 83 elements of the periodic table in samples of various forms and nature: solids or liquids, conductive or non-conductive. Advantages of XRF over other techniques are speed of analysis, generally easy sample preparation, very good stability, precision and wide dynamic range (from ppm levels to 100 %).
Accuracy of analysis of powders can be impaired by particle size effects and mineralogical effects. Although inhomogeneities and particle size effects can often be minimised by grinding below 50 µm and pelletising at high pressure, often mineralogical effects cannot be completely removed, or harder particles cannot be broken down below the required size.
Fusing these oxidic materials is the best way of completely removing both grain size and mineralogical effects. Essentially, the procedure consists of heating a mixture of sample and a borate flux, namely lithium tetraborate and/or lithium metaborate at high temperature (1000–1200°C) so that the flux melts and dissolves the sample. The overall composition and cooling conditions must be such that the product after cooling is a one phase glass.