X-RAY FLUORESCENCE Research Technical Services

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Research Technical Services

X-RAY FLUORESCENCE

X-ray fluorescence (XRF) is the emission of characteristic "secondary" (or fluorescent) X-rays from a material that has been excited by bombarding with high-energy X-rays. When materials are exposed to short-wavelength X-rays, ionization of their component atoms may take place. Ionization consists on the ejection of one or more electrons from the atom, and may take place if the atom is exposed to radiation with energy greater than its ionization potential. X-rays can be energetic enough to expel tightly held electrons from the inner orbits of the atom. The removal of an electron in this way renders the electronic structure of the atom unstable, and electrons in higher orbits "fall" into the lower orbital to fill the hole left behind. In falling, energy is released in the form of a photon, the energy of which is equal to the energy difference of the two orbitals involved. Thus, the material emits radiation, which has energy characteristic of the atoms presented. The intensity of the characteristic radiation is proportional to the concentration of the element in the sample.

 

 Applications

The phenomenon is widely used for qualitative and quantitative elemental analysis, particularly in the research of metals, glass, ceramics, building materials, and in geochemistry research, forensic science and archaeology. The elements to be analyzed are from the F to U, in solid or liquid samples. The excluded elements are H, Li, 61Pm, 43Tc, 84Po, 85At, noble gases (except Ar) and the actinium group from the 89Ac to 103Lr (except 90Th and 92U). To complement the qualitative analysis, the software package IQ+ can be used to realize semi-quantitative analysis in all kind of samples. The IQ+ corrects the usual spectral interferences and the matrix effects for fundamental parameters.

 Equipment

Fluorescence X-rays

An X-ray sequential spectrometer PHILIPS MAGIX PRO equipped with a rhodium x-ray tube and beryllium window is used. PW2400 spectrometer is a sequential instrument with a single goniometer based measuring channel, covering the complete measuring range. In addition, up to two fixed channels may be fitted in the MagiX PRO giving a limited simultaneous capability.

The instrument is microprocessor controlled for maximum flexibility. The whole system is controlled from an external computer, running the analytical software package. In addition to these assemblies, the system includes a number of options and external peripherals like sample chargers and modem (for remote control).

The analytical software package is SuperQ. It is a suite of programs, which together allow us to measure and analyse samples using Philips MagiX PRO X-ray spectrometers.

SuperQ controls the spectrometer, stores the measurements results in a database, processes the results using a variety of methods and can present the results in various ways. Within the software, application knowledge in already implemented resulting in an easy to use spectrometer system.

The modules of the program that are included in the suite are:

 

FEDER

Sample requirements

 

For the analysis of a piece is to get into a cylinder of 5 cm in diameter and 4 cm in height.

For powder samples is essential to a uniform particle size, between 10-20 microns

Analysis on dust will require one sufficient amount of sample to cover a holder of 27 mm in diameter (1 hour) or at least a sample of 6 mm in diameter (1.5 hours).

For analysis in pill form (trace) will be necessary 10 grams of sample.

For analysis in Pearl (over) a minimum of 1 gram of sample will be required.

Database utilities