Enrichment and purification of trace substances from yew extracum by twin-column recycling chromatography with a step solvent gradient.

The concentration and purification of trace substances from natural products represent a bottleneck in current chromatographic separations. In this study, a twin-column recycling chromatography with a step solvent gradient method was proposed and successfully applied in the purification of unknown substances with tiny content in yew extracum. The method consists of two steps.

Gas adsorption and separation in metal-organic frameworks by PC-SAFT based density functional theory.

In this work, we examine the theoretical performance of perturbed-chain statistical associating fluid theory based density functional theory (DFT) in predicting gas adsorption and separation in metal-organic frameworks by using simulation and experimental data as the benchmark. Adsorption isotherms of methane and ethane in pure gas and mixtures and selectivities for ethane/methane mixtures are calculated. The predicted isotherms by DFT are in excellent agreement with simulation and experimental data for pure methane and ethane, whereas for the mixture, DFT is in semi-quantitative accordance with simulation results.

Theoretical study of twin-column recycling chromatography with a solvent-gradient for preparative binary separations.

Twin-column recycling chromatography with a solvent gradient (TCRC-SG) was investigated with the equilibrium-dispersive chromatography model. The solvent gradient caused by constant addition of a modifier between the two columns created a band compression effect to counterbalance band broadening, so that the target component band neither broadened nor shrunk. Meanwhile, band compression accelerated the separation but prevented excessive separation.