Pre-treatment of diffuse reflectance infrared spectra for quantitative analysis of macro porous polymer particles

A general pre-treatment procedure for diffuse reflectance infrared spectra is developed for quantitative analysis of macro porous polymer particles. S everal different procedures for pre-treatment of diffuse reflectance infrar ed spectra are compared. Different samples with replicated spectral measure ments from manual packing as well as from automatic packing were investigat ed in order to define the best pre-treatment procedure. Excellent results a re obtained by the following four-step procedure: (i) use the packing unit in order to reduce deviations due to surface differences for different pack ings, (ii) define a zero-absorbance range (100% in reflectance spectrum) or some unchanged peak region to normalise the spectra in order to eliminate deviations between different packings, (iii) correct baseline of the reflec tance spectrum peak by peak, and, (iv) finally, transform the baseline-corr ected reflectance spectrum into Kubelka-Munk format. The diffuse reflectanc e spectra so obtained can be then utilised in quantitative analysis, since the relative deviations between the repeatedly measured spectra after this pre-treatment are lower than 5%. (C) 1999 Elsevier Science B.V. All rights reserved.