Photoacoustic FT-i.r. spectra of separated western Canadian coal macerals

Several authors have analysed the CH stretching regions of infrared spectra of coals using numerical methods to increase the resolution of the component bands. The results of these studies differ widely with regard to the number of bands, in addition to their shapes, positions and widths. This paper reports the results of an investigation in which some of these techniques have been applied to photoacoustic FT-i.r. spectra of the vitrinite, resinite and fusinite macerals separated from a subbituminous western Canadian coal. The spectra were analysed by non-linear deconvolution and curve-fitting, with the requirement that the results obtained by the two methods be consistent with each other. Thus, it was concluded that Voigt functions consisting of approximately equal Lorentzian and Gaussian contributions provided the best description of the bands. The number of bands that could be confirmed in the aliphatic and aromatic CH stretching regions of the spectra varied between 11 and 13 for the three macerals. Assignments of almost all of these bands were made by reference to the literature.