APPLICATION OF REFLECTANCE MICRO-FOURIER TRANSFORM-INFRARED SPECTROMETRY IN STUDYING COAL MACERALS - COMPARISON WITH OTHER FOURIER-TRANSFORM INFRARED TECHNIQUES

The applicability of the reflectance micro-Fourier transform infrared (FT-i.r.) technique to analyse the distribution of functional groups in coal is discussed. The spectra of a series of coals from lignite to anthracite obtained using reflectance micro-FT-i.r. were compared with those of the same materials but obtained using transmission micro-FT-i.r. and KBr pellet techniques. This comparison shows that (1) band absorbances in the transmission mode are much higher than those in the reflectance mode; (2) band peak positions are the same in the transmission and reflectance modes as long as Kramers-Kroning transformation is applied; and (3) the 700-900 cm-1 aromatic-dominated region has higher absorbance in the reflectance than transmission mode. Reflectance spectra and KBr pellet technique spectra compare very closely; band absorbances and band locations are the same or almost the same. The main difference between reflectance micro-FT-i.r. and KBr pellet techniques is a much higher absorbance in the 700-900 cm-1 region in the reflectance mode. The results indicate that reflectance spectra can be utilized to characterize functional groups in organic matter under most conditions. The ease of sample preparation, the potential to analyse large intact samples and the ability to characterize areas as small as 30 mum are the main advantages of reflectance micro-FT-i.r. The quantitative aspects of reflectance micro-FT-i.r. require further study.