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1.
Separation of parthenolide from feverfew: performance of conventional and high-pressure extraction techniques
Lucija Čretnik, Mojca Škerget, Željko Knez, 2005, original scientific article

Abstract: In present work the extraction of feverfew flower heads was performed using supercritical carbon dioxide at pressures from 200 to 800 bar and at temperatures of 40, 60 and 80 °C. For comparison, the conventional extractionswith organic solvents have been performed. Dry feverfew flower heads were used as starting material. Supercritical fluid extraction (SFE) wasperformed using a semi continuous flow apparatus in a laboratory and pilot scale. The influence of process parameters on the total yield and amount of parthenolide isolated was investigated. Dynamic behaviour of the extraction runs followed by single-step separation was analysed by a mathematical model for initial constant rate extraction period and the subsequent time-dependant diffusion controlling mass transfer rate period. In order to concentrate the obtained extract in parthenolide, a two-step separation was employed.
Keywords: chemical processing, high pressure extraction, conventional extraction, supercritical CO2, parthenolide, feverfew, extraction rate, mass transfer
Published in DKUM: 01.06.2012; Views: 1919; Downloads: 105
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2.
Influence of the aromatic ring substituents on phase equilibria of vanilins in binary system with CO2
Mojca Škerget, Lucija Čretnik, Željko Knez, Maja Škrinjar, 2005, original scientific article

Abstract: Solid-liquid phase transitions of vanillin, ethylvanillin, o-vanillin and o-ethylvanillin in presence of compressed CO2 were determined with the modified capillary method. Furthermore, the solubilities of the above mentioned vanillins in supercritical CO2 were measured at 313.2, 333.2 and 353.2 K and in the pressure range 8-30 MPa using a static-analytic method. The experimental equilibrium solubility data have been fitted to the Peng-Robinson equation in combination with two parameter van der Waals mixing rules and binary parameters were determined from the best fit. Results showed that the phase equilibria of vanillins in dense CO2 are influenced by the position of the hydroxyl group bound to the aromatic ring. Under the pressure of CO2 the melting point depression and also the solubility of both o-vanillins was higher than those of p-vanillins. Oppositely, the alchoxy group (methoxy or ethoxy) showed no significant influence on the solubility of vanillins.
Keywords: chemical processing, high pressure technology, CO2, phase equilibria, vanillin isomers, data, ring substituents
Published in DKUM: 01.06.2012; Views: 2067; Downloads: 47
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