X-ray fluorescence (XRF) is an analytical technique which uses the interaction of x-rays with a target material to determine its elemental composition. XRF is a totally safe, non-destructive method. The technology of the analyser is based on energy dispersive X-ray fluorescence using an X-ray tube as the source of excitation. The range of detectable elements varies according to the individual instrument’s configuration, but typically EDXRF covers all elements from sodium (Na) to uranium (U).
Concentrations can range from ‘100%’ down to ‘ppm’ (and in some cases sub-ppm) levels. XRF is a “non-destructive” process, which means there is no need to physically scrape, remove or damage the sample item to determine the outcome. XRF spectrum analysers are widely used in Industries as diverse as precious metals, alloys, toys, electrical/ electronic, environmental and mining.
X-ray fluorescence involves the emission of characteristic fluorescent Xrays from a material which has been excited by bombarding it with highenergy X-rays or gamma rays. X-ray fluorescence can be considered as a simple, three-step process occurring at the atomic level. First, an incoming X-ray knocks out an electron from one of the orbital’s surrounding the nucleus within an atom of the material.
A ‘hole’ is produced in the orbital, resulting in a high- energy unstable configuration for the atom. To restore equilibrium, an electron from a higher-energy, outer orbital falls into the hole. Since this is a lower energy position, the excess energy is emitted in the form of a fluorescent X-ray. This is the ‘Energy Dispersive’ aspect of the process and it is this energy which is measured by the equipment.
The difference in energy between the expelled and the replacement electrons is characteristic of the element atom in which the fluorescence process is occurring – thus, the energy of the emitted fluorescent X-ray is directly related to the specific element being analysed. It is this key feature which makes XRF such a fast analytical tool for elemental composition.