Wavelength dispersive X-ray fluorescence, WDXRF
Another method used for the elemental analysis in petroleum products is wavelength dispersive X-ray fluorescence to determine total amount of sulphur in petroleum products. This technique is sensitive and selective for elemental analysis. All the elements in the sample are excited simultaneously and the energy radiations emitted from the compound are diffracted on the monochromator. An analyzing crystal is used to disperse the intensity of emitted photons by diffraction on to the detector. The wavelength intensities are collected by a computer system that is then compared to a calibration curve. The drawback of a WDXRF system is that it requires a high-power X-ray tube in a complicated system, at extra expenses. This instrument is very expensive and requires a standard matrix to perfectly match with the sample matrix since carbon and hydrogen ratio differences or other interfering species can lead to false results. It is not suited for field testing where bulky samples need to be quickly analyzed. This technique is very good for higher detection limits of elemental analysis and for less bulky samples.