Correlation of countercurrent extraction with countercurrent chromatography in aqueous matrixes. An improved model

Abstract

A mathematical model was employed to simulate supercritical fluid extraction (SFE) efficiency in aqueous matrixes with supercritical fluid chromatography (SFC) data in a previous study. The SFE extraction vessel, i.e., the column for the SFC, was mathematically divided into limited layers. The analyte mass was uniformly distributed in the vessel before extraction. However, it changed when the fluid flowed through the aqueous sample and reached the column outlet. The mass redistribution as a function of the layer was computed using a countercurrent distribution approach. Afterward, each layer was considered to undergo a chromatographic process simultaneously. Each layer's chromatographic capacity factor and peak width were calculated using the true SFC experimental data, and the sum of all these peak distributions as a function of time gave the extraction efficiency, In this work, the mass redistribution was calculated through a chromatographic approach, which predicted the extraction recovery better than the previous approach,,Both the previous SFE and the newly acquired liquid/liquid extraction data using a countercurrent chromatographic apparatus were examined to demonstrate the upgrading of the model using this new chromatographic approach. Significant improvements were observed, especially for analytes with small capacity factors. The simulation deviations came mainly from the fact that analyte molecules in the individual layers would shift away from Gaussian shapes that were assumed in the model.