Application Of Supercritical Fluid Extraction In Organic Geochemistry

This thesis systemically summarize property of the supercritical fluid, and principle, characteristic, advantage and development of the supercritical fluid extraction (SFE) technique, and at the same time, research progress and developing potential have also been reviewed, particularly in organic geochemistry. Based on this, we have chose some of appropriate geological samples for dynamic analysis by use of the HP 7680T SFE (made by USA) at high press and lower temperature. The instrument is automatically controlled by a computer at controlling pressure, temperature and methanol used as a modifier. The analytical results from SFE/GC-MS was then compared with those from the traditional Soxhlet extraction (SE)/GC-MS, and the following conclusions can be suggested:a. The biomarkers extracted from ancient consolidated mudstoneThe mudstone selected for this study is with lower content of organic carbon (i.e., total organic carbon is less than1.5%), and SFE and SE were used as extracting methods, respectively, for comparisons of the alkanes, terpenes, steroids in biomakers, suggesting the distributions, mass spectrometer feature and geochemical parameters of the biomarkers by SFE is in accordance with those of the SE method. Therefore, SFE method can be used as analyzing the biomarkers in mudstone and other consolidation samples. Although some authors have previously done some studies for the biomarkers from some samples, such as coals and oil-shales, with higher content of organic carbon by SFE, this study has extended the availability of SFE method for the samples with lower content of organic carbon.b. The biomarkers of modern lake sediments from Antarctica:We have analyzed some biomarkers, such as alkane, hopanes, steroids anda series of unidentified compounds with apparent m/z 94 by use of SFE and off-line GC-MS. The results, compared with data from previous researchers doing some samples similar to current those by SE method have shown very close coherence, particularly the recognizing a serious of the compounds with m/z94. The study of the biomarker in modern sediments by SFE will provide very significant information for discerning the source of the organic matter and tracing their biogeochemical process. In addition, lower content of organic carbon (average 0.18%) in the samples suggest that SFE can be used as extracting trace organic components in geological samples due to high efficient, rapid and strongly selective advantage.c. Removing of organic esters in extracting cellulose from peat plants:SFE has been used to removing of organic esters in extracting cellulose from peat plants is a renovating method, different from traditional thinking, and extend its applicant fields for this technique. The components including organic acids and their methyl esters, some alkanes have been removed out from peat plants by SFE. The extracting process is easy, rapid, and in lower temperature, and with some advantages than SE method, such as quick, safe to any samples. So it provide significant guarantee for obtaining primary stable isotopic information from the cellulose, and can be used in environmental geochemistry for extraction and separation of organic esters.In conclusion, the SFE technique has made important progress in preparation and separation of the biomarkers from various geological samples due to many advantages such as rapid, easy, high efficient, safe, automatic and strong selective etc. In the whole work, the analysis of biomarkers from both ancient consolidation mudstones and modern sediments (lake sediment and peat deposit) is successful , indicating wide potential in research of organic geochemistry.