Abstract
Thermodesorption technique coupled on-line with gas chromatography (GC) and mass spectrometry (MS) has been developed for the determination of hydrocarbons trapped in coal and rock samples. The method can also be applied to the determination of volatile constituent present in biological materials. The desorption step is carried out in the pre-heated injector of a gas chromatograph. The mobilized compounds are transferred without splitting to the initial part of a cold GC column. After 10 min of desorption the GC—MS analysis is started. The identification of individual compouds is achived by GC—MS analysis of related molecular ions or significant fragment ions. When micro-samples (0.25–2.0 mg) of dried plant material are heated to 300°C in a helium stream. compounds such as long-chain fatty acids, carboxylic acid esters, aldehydes and ketones as well as steroids and tocopherols are desorbed from the biological matrix decomposition. In addition, the thermally chlorophylls decompose to yield phytadienes as pyrolysis products of the phytyl moiety. The phytadienes can be used to estimate the original algae and terrestrial plant materials. This ratio partly reflects the pristane:phytane concentration ratio determined in extracts of mature sediments rich in related fossilized biological materials. The analysis also provides chemotaxomic information about the sterol composition of plants.
Published Version
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