SUPERCRITICAL CARBON-DIOXIDE EXTRACTION OF LONG-CHAIN ALIPHATICS FROM 2 SOILS

Current trends in soil organic-matter research are focused on developing methods for the extraction of specific organic-matter components. One such method is the supercritical gas extraction of soils using CO2. To examine the applicability of this approach to whole soils, we used supercritical CO2 for extracting two soils. The resulting extracts were analyzed by chemical methods, infrared (IR), C-13 nuclear magnetic resonance (NMR), and by field-ionization and field-desorption mass spectrometry. Major components identified in the extracts were C-15 to C41 n-alkanes, the C8 alkene, the C20 n-alcohol, C-14 to C40 n-fatty acids, C-17 to C41BAR unsaturated fatty acids, the C18 and C26 dioic acids, the C28 and C30 n-ketones, C38 to C64 n-alkyl monoesters, the C52 n-dioic acid dimer, and the C78 n-dioic acid trimer. Of special interest was the presence in the extracts of 10-nonacosanol (C24), a biomarker for coniferous epicuticular waxes. Supercritical CO2 was found to be a mild and specific extractant for the removal of long-chain aliphatic materials from soils.