Compound APFs
The first option calculates a compound APF correction based on binary APF factors for an element in a binary standard (for example O ka in Cr2O3) and sums all binary APF factors based on the weight fraction of the emitting element to create a “compound” APF that applies to the specific analyzed composition. This is ideal in cases where all the elements affecting the emitting element have measured binary (end-member) APF factors. The calculation for compound APFs is shown here:
Where:
is the binary (end-member) APF
for elements other than the affected element
is the weight fraction for
elements other than the affected element
is the sum of all elements other
than the affected element
A further normalization is performed on the compound APF to ensure that in situations where the partial sum is very low, the compound APF is not over applied to the affected (pure) element when only the trace elements are varying in precision. This calculation is show here:
Note that this APF normalization correction is only applied when the absolute value of the scaling factor :
is greater than or equal to 1.0 to avoid problems with over applying the correction on major elements.