Extraction of biomarkers from sediments with supercritical carbon dioxide : a comparative study with solvent extraction and thermodesorption methods

Supercritical fluid extraction of rocks with CO2 (SFE-CO2) can advantageously replace the organic solvent extraction technique (SE) which is generally used for the analysis of the biomarkers. The powdered rock is extracted by carbon dioxide supercritical fluid at 55°C and a pressure of 31 MPa. After decompression in a capillary restrictor, the CO2 is volatilized and the extracted compounds are trapped in hexane. An aliquot can then be directly injected into a dual GC-FID-FPD or GC-MS system. The total extraction procedure takes only 45 min and the results obtained for hopanes and steranes are in very good agreement with those of liquid solvent extraction, which requires several hours. A comparison with thermodesorption is also presented.