ZAF
A method for the matrix correction of emitted (as opposed to generated) x-rays from a sample. The method calculates the effects of atomic number (Z), absorption (A) and characteristic (and sometimes continuum) fluorescence (F) separately, hence the name ZAF. To put all of this in perspective, here is the complete ZAF correction expression for x-ray intensities solved for the concentration of an unknown concentration :
where : 
is the unknown k-ratio
and
is the ZAF correction factor of the unknown
is the unknown intensity for element A at λ
is the standard intensity for element A at λ
is the concentration of the element in the standard
is the ZAF correction for the element in the standard
Because the ZAF correction factor for the unknown is exactly that : unknown, the calculation requires a iterative solution. See also Phi-Rho-Z.