1. I am still not satisfied with selected SO2 value (it is set to 0.85). SO2 is not transferable between different samples and detection methods. It is not possible to use a value obtained from different compound using transmission measurement mode to completely different other compound measured using fluorescence mode. One method to fix SO2 value is to measure diluted solution (to avoid self-absorption) of reference material in fluorescence mode. Other is to use multiple spectra fitting for all samples of interest (e.g. with Sb(V)) measured using fluorescence mode where SO2 parameter is the same for all samples.

At the same time I am confident that CN values 5.6, 7.1 and 6.9 correspond to CN(Sb-O)=6. I suggest reconsidering the SO2 value for measurements in fluorescence mode.