X-ray fluorescence (XRF) analysis is a technique that exploits the unique interaction between primary X-rays and matter. All matter is made of atoms and at the centre of every atom is a nucleus, which is positively charged due to the presence of protons (+ve charge) and neutrons (no charge). Electrons (-ve charge) orbit the nucleus in discrete quanta known as shells. Their total negative charge balances out the positive charge of the nucleus, rendering the atom neutral. This can be altered by introducing external energy, such as X-rays. X-rays are subvisible waves of light with very short wavelengths, thus very high energy, which are absorbed while passing through substances – depending on the composition and density of the substance.
When an atom is struck by an X-ray with enough energy (exceeding the atom’s shell binding energy), an electron within its innermost orbital shells is ejected, creating a vacancy. An electron from a higher atomic orbit will drop down to the vacancy in this lower energy state. This requires an emission of energy in the form of fluorescence, or secondary X-rays, which equals the specific difference in energy between the electron’s two quantum states.
Secondary X-rays are characteristic to individual elements in the periodic table. When a sample is analysed via XRF, every element present will emit these unique X-ray signals in the form of a spectrum. This spectrum, also known as an elemental fingerprint, is central to the performance of both EDXRF and WDXRF.
Obtaining a legible XRF spectrum can be complicated by a number of limitations (Rayleigh or Compton scattering, spectral effects, matrix effects, etc.). To ensure accuracy of results, it is often critical to perform empirical calibration or Fundamental Parameters (FP) analysis.
In EDXRF analysis, the characteristic X-rays of different elements present in a reading are separated into a complete fluorescence energy spectrum using either direct excitation (2D optics) or indirect excitation (3D optics). You can learn more about each of these excitation geometries by downloading our guide posters using the forms below. EDXRF technology is engineered to simultaneously process whole groups of elements for qualitative or quantitative analysis and can be used in portable and laboratory-based formats. As a result, EDXRF can accommodate samples of almost any shape and size.
WDXRF is preferred to EDXRF for high resolution applications (~15-150 eV) and analysis of lower atomic mass elements and rare earths. Rather than process a complete spectrum, WDXRF separates fluorescent signals into individual wavelengths using crystals and a series of optical components (collimator, optical encoders, detectors, etc.).
Both EDXRF and WDXRF are robust solutions in their own right, performing key functions in markets as varied as metals and alloys manufacturing, petrochemicals, forensics, food analysis, environmental analysis, and much more.
