EFFECT OF THE MATRIX ON THE KINETICS OF DYNAMIC SUPERCRITICAL-FLUID EXTRACTION

A model for dynamic supercritical fluid extraction (SFE) is proposed, which contains the steps of: rapid fluid entry into the matrix; a reversible release process such as desorption from matrix sites or penetration of a biological membrane; transport, by diffusion or otherwise to the edge of a matrix particle; and removal by solvation in the fluid. It can explain the following kinetic features of dynamic SFE: (i) a slow initial extraction; (ii) a more rapid extraction phase; and (iii) a slow final phase, which can be so slow that it appears that extraction is complete when only a fraction of the solute present in the matrix has been recovered. The model may be used to extract values for the parameters quantifying the individual steps, to understand further the SFE process.