The traditional use of X-ray fluorescence analysis (XRF) has its roots in geology. Solid samples were the first sample types analyzed by X-rays. Over the years the applications expanded and nowadays the applications cover the analysis of alloys, various types of powder samples to liquid samples and filter material.
The principle of XRF
The effect of X-ray fluorescence is based on the excitation of atoms in the sample. A primary X-ray, typically generated in an X-ray tube, hits an inner shell electron of the atom and ejects the election from the atom. The open position is filled by an electron from a further outer shell and fluorescence radiation is emitted. The fluorescence energy is equal to the energy difference between the two election shells. Therefore, the energy of this radiation is characteristic for the atom and indicates, what atom is present in the sample.
As many atoms are present in the sample, it will emit various X-rays with different energy. In an energy-dispersive XRF instrument the fluorescence radiation is collected by a semi-conductor detector. The X-rays create signals in the detector, which are depending on the energy of the incoming radiation. The signals are collected in a multi-channel-analyzer.
This process handles each X-ray one by one but with a high speed. A detector of a modern XRF machine can handle 1 million counts per second. This makes it a quasi-simultaneous measurement. Even with a short measurement time, the spectrum can give sufficient information to calculate intensities, which can be used to determine the composition of the sample. Using a longer measurement time allows for better statistics resulting in better precision and better peak-to-background thus resulting in improved detection limits.
For a highly precise analysis of an element present in the sample minimum a few million counts should be collected. This is quite easy if the sample contains a high concentration of an element and the detector can handle a high count-rate, but will be more difficult if concentrations are low and detection system are only able to handle a low count rate.
This XRF principle video presents an easy-to-understand introduction into the physics and the technology of an XRF analyzer. You can find more detailed information by requesting the featured whitepapers below. They will give you additional information about X-ray fluorescence spectroscopy as well as the benefits of an advanced XRF spectrometer. Find out more about our comprehensive portfolio of advanced XRF spectrometers.