Quantitative analysis requires that a number of corrections be made to the raw data. The initial intensity data (counts) must be corrected for deadtime, background and instrumental drift, prior to making the matrix corrections for inter-element effects. All intensity data is then referenced to standards and presented as a ratio.
The corrected intensity ratio of an element's X-ray line is not directly proportional to the concentration of the element because the ratios are affected by X-ray absorption, secondary fluorescence, electron backscattering, and the electron stopping power of the sample. There are several methods of taking these factors into account and determining concentrations: Calibration curves, which use an empirically determined relationship between counts and concentration; Bence-Albee, which uses empirically determined correction coefficients or a factors; and ZAF or PAP, which use fundamental factors to correct for the effects of atomic number, absorption and fluorescence. These methods are summarized below. Those wishing more detail should examine one of the references.
Copyright 1997-2003, James H. Wittke
Last update: 01/18/2006 01:47 PM.