Comparison between EDXRF and WDXRF

Another significant difference is in spectral acquisition. With an EDXRF system, the entire spectrum is acquired simultaneously within a few seconds. In a WDXRF system, the spectrum is acquired point by point, which requires more time. The alternative, a simultaneous WD system such as has been described, is very expensive. 

Modern WDXRF instruments permit the determination of all elements from fluorine (Z = 9) to uranium (Z = 92). Some WDXRF systems allow measurement of elements from Be to U. Benchtop EDXRF instruments can determine elements from sodium (Z = 11) to uranium (Z = 92) with a special SDD detector, it is possible to measure from fluorine to uranium. Handheld EDXRF units with SDD detectors can measure from magnesium (Z = 12) to uranium, and Si-PIN units can do the same with vacuum or He purge. 

Elements with atomic numbers between Mg (Z = 12) and U (Z = 92) can be analyzed in air. Elements with atomic numbers 3 (beryllium) through 11 (sodium) fluoresce at long wavelengths (low energy), and air absorbs the fluorescence. Analysis of this group must be carried out in a vacuum or in a helium atmosphere. 

WDXRF units usually operate primarily under vacuum and use a helium atmosphere for loose powder samples and liquid samples. Benchtop EDXRF and micro-XRF systems can operate under vacuum, helium, or air, based on the configuration. Handheld or portable units generally operate in air at atmospheric pressure. 

The DLs are in the ppm range for most elements with a wide linear working range. XRF thus permits multielement analysis of alloys and other materials for major, minor, and trace elements. Sensitivity is poorest for the low Z elements and best for the high Z elements. XRF capabilities are dependent on the technique (ED or WD used) as well as the power and other design variables of the actual instrument employed. 

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