Solubilities of the fat-soluble vitamins A, D, E, and K in supercritical carbon dioxide

Solubilities of eight different species of the fat-soluble vitamins A, D, E, and K in supercritical carbon dioxide were measured at (313, 333, and 353) K and over a pressure range of 20 MPa to 35 MPa. Solubilities have been determined by an analytical method using the direct coupling of an equilibrium cell to a supercritical fluid chromatographic system with UV detection. The solubilities of all fat-soluble vitamins in supercritical carbon dioxide under the conditions investigated are in the range of 10 g/kg, except for beta-carotene (provitamin A), which is 3 orders of magnitude less soluble. With increasing molecular mass of the vitamin, its solubility in supercritical carbon dioxide decreases. At constant temperature, the solubility of all substances increases with increasing density. At constant density, a rise of temperature results in an increase in solubility. This is caused by the increasing vapor pressure of the solid.