THERMAL-DESORPTION AS AN ANALYTICAL TECHNIQUE IN BIOMARKER ANALYSIS OF IMMATURE COALS

Applications of the thermal desorption (TD) technique to a suite of immature coals are described. The thermal desorption temperature is defined as just below the temperature at which n-alkenes < C21 appear in a gas chromatogram. TD and solvent extracts are shown to be almost identical on gas chromatographic analysis. Advantages of TD are presented, and include its potential for rapidly and easily "fingerprinting" samples for structurally free maturity biomarkers; the fact that it maximizes differences in composition between samples; and its capacity, when combined with single ion extraction, to allow rapid scanning for maturity indicators and a partly quantitative but direct comparison of the di- and triterpenoid composition of samples. Thermally sensitive structures are stable to TD: seco-triaromatic triterpenoids are released on TD but are not seen at higher pyrolysis temperatures; and the retention of stereochemistry of biomarkers on TD is a distinct advantage of the technique. © 1990.