CONCENTRATION-DEPENDENCE OF THE RELATIVE ERROR IN DIFFUSE-REFLECTANCEINFRARED SPECTROMETRY

A mathematical model between the relative error in the Kubelka-Munk (K -M) function and the sample concentration has been determined if the K -M function is linear with the sample concentration, c less than or eq ual to 1 w/w%. The theoretical model has been investigated by measurin g 3-5 parallels at different sample concentrations and calculating the RSD for the selected absorption bands. Quartz (d(ave)=1.3 mu m) and c alcite (d(ave)=3.3 mu m) as analytes and KBr (d(ave)= 9.9 mu m) as emb edding material were used. The result of the model and the experiments were in a good agreement. It has been shown that the RSD for absorpti on bands with smalt sensitivity can increase up to +/-20-60%. The prec ision of the quantitative analysis in diffuse reflectance infrared Fou rier transform spectrometry (DRIFTS) can be improved by applying more sensitive absorption bands and parallel measurements at one standard c oncentration.