Application of GC-MS chromatography for the analysis of the oil fractions extracted by supercritical CO₂ at high pressure

GC-MS chromatographic analysis has been applied for the investigation of the fractions of oil extracted by supercritical carbon dioxide at a temperature of 60 °C and at pressure values ranging from 22 to 56 MPa. The observations revealed, that the whole extraction process is clearly reflected in the chromato-grams, demonstrating how the heavier hydrocarbon fractions were gradually involved in the extraction process. The shape of the chromatograms alters with increasing pressure from triangle to trapezoid, approaching the shape of the chromatogram of the crude oil. The observation of the fingerprints of chromatograms allows them to be used for the qualitative evaluation of extraction progression. It can also be noticed, that the area under the spectrum of the chromatograms of oil samples extracted at various pressures is increasing with an increase in pressure. The oil recoveries, evaluated as the ratio of the area under the spectrum or the baseline of the chromatogram of the sample extracted at the specific pressure value to the area under the spectrum or the baseline of the chromatogram of the crude oil, showed a close correlation with the oil recoveries obtained from the experiment. This allows the use of the chromatographic method for the quantitative evaluation of oil recovery.