Regional Geochemical Centre

X-Ray Spectroscopy

Analytical X-Ray Spectroscopy (XRF)


xrayImage1When incident X-rays strike an object they can interact with it in several ways. They can be photoelectrically absorbed, scattered or cause fluorescence. Absorption is the basis for medical X-rays and security screening and scattered X-rays are used to determine crystal structure. Fluorescence is the formation of secondary X-rays by the object being exposed to the primary source. The wavelength of these secondary X-rays are dependent upon which elements are present in the object, and the intensity of each depends on the concentration. This is the basis of analytical XRF. Specimens are exposed to a primary high intensity x-ray source and the resulting secondary X-rays are collected by detectors and quantified using computer algorithms together with standard reference compounds; and corrected using theoretically determined coefficients or matrix effects, whichever is more appropriate.

The Philip's PW2400 x-ray Spectrometer

The main instrument in the Regional Analytical Facility is the Philips PW2400 x-ray spectrometer with the Philips PW2510 102 position sample changer. The PW2400 is a wavelength-dispersive sequential spectrometer, which utilizes a 3kW Rh anode to produce a continuum of primary X-rays used to excite the sample. The fluorescing wavelengths from the sample are separated using natural and synthetic crystals and the photons captured by either a flow detector or a scintillation counter. The entire process is controlled by microprocessor with minimal input from the analyst. All results are fully corrected both for machine drift and matrix effects.