Horsetail (Equisetum giganteum L.) oleoresin and supercritical CO2: Experimental solubility and empirical data correlation

The solubility of horsetail (Equisetum giganteum L.) oleoresin in supercritical CO2 was investigated. The experiments were carried out using the dynamic method at different temperature (20, 30 and 40 °C) and pressure (12, 15 and 20 MPa) levels, indicating a solvent density ranging from 719.1 to 937.5 kg/m3. By using low solvent flow rates, it was assumed that the solvent was saturated with the solute downstream the extractor. The results of the solubility experimental data, obtained for the operating conditions evaluated in this work, varied from 2.33 × 10−4 to 5.23 × 10−4 g/g CO2. The experimental results were correlated using three different empirical equations proposed correspondingly by Chrastil, del Valle and Aguilera and Gordillo et al. The lowest deviation between experimental data and correlated values was obtained from the results taken at 40 °C and using the correlation proposed by Gordillo et al. (1999).