EDAX EDS Manual

Although this is commonly not an easy thing to do, the quantitative analysis actually
does this comparison in its calculation (this is shown graphically in Fig. 2 below).
Fig. 2. Same spectrum as in Fig. 1 (shown in solid black) compared to the outline of
the pure element intensities for each element.
The ratio of the element’s peak height in a sample to the pure element collected under
the same conditions is actually used in the quantitative calculation as the k-ratio. All
other steps in the quantitative analysis with and without standards are identical and the
only difference is whether the pure elements are actually measured (with standards) or
are calculated (standardless). Before the k-ratios are calculated, the peaks are
identified, a background is fit, a peak-fitting routine is used and overlapped peaks are
deconvoluted, and the net count intensities are measured. After the k-ratios are
calculated, the ZAF corrections are applied, where: Z is an atomic number correction
which takes into account differences in backscattered electron yield between the pure
element and the sample (high atomic number pure elements will produce fewer x rays
because some of the beam electrons leave the sample before losing all of their energy);
A is the absorption correction which compensates for x rays generated in the sample but
which are unable to escape when they are absorbed within the sample (low-energy x
rays tend to be heavily absorbed); and F is the fluorescence correction which will correct
for the generation of x rays by other x rays of higher energy. In order to calculate the
ZAF factors, the composition must be known, but we need to know the ZAF factors to
calculate the composition. This apparent contradiction is resolved by calculating ZAF
EDAX Training Course - Quantitative Analysis - page 2