QUANTITATIVE-ANALYSIS OF POWDERED ORGANIC-MATTER BY TRANSMISSION INFRARED MICROSPECTROSCOPY USING A DIAMOND-WINDOW COMPRESSION CELL

An artificial coalification series of Mahakam coal (type III organic m atter) was analysed by transmission FT-i.r. microspectroscopy using a diamond anvil compression cell. Micro-infrared spectra were compared w ith spectra recorded in global mode using the standard KBr pelletizati on technique. Results indicated that infrared microspectroscopy provid es higher-quality spectra (baseline and signal/noise ratio) as well as more information (accurate OH and nu aromatic CH integration) than th e bulk approach. The interference fringes on the micro-infrared spectr a were used for sample thickness determination. Direct application of the Lambert-Beer law then allowed the absorbances of major infrared ba nds to be used to reveal the chemical changes taking place during matu ration. Aliphatic CH species were shown to decrease roughly linearly w hereas aromatic CH increased exponentially with increasing pyrolysis t emperature. The end member of the artificial coalification series exhi bited a fourfold lower aliphatic content and fifteenfold higher aromat ic content than the original sample. Although oxygenated functions (OH , C-O and C=O) were substantially removed during the maturation, the c ontrasted behaviour of individual C=O bands (1710, 1735 and 1650 cm(-1 )) strongly suggested a rearrangement among the C=O functions during a rtificial coalification. Direct absorbances of selected infrared bands were plotted against widely used geochemical parameters (H/C and O/C atomic ratios and Rock-Eval hydrogen index). The good correlations obt ained indicate that transmission infrared microspectroscopy using a di amond anvil compression cell is a promising technique for statisticall y deducing the WC, O/C and HI values of kerogen. (C) 1997 Elsevier Sci ence Ltd.