Solvent strength of organic phase for two biphasic solvent systems in high speed countercurrent chromatography.

In this work, relationships between solvent strength of organic phase (ψ) for two biphasic solvent systems in high speed countercurrent chromatography, hexane-ethyl-acetate-methanol-water (HEMWat) and ethyl acetate-n-butanol-water (EBuWat), and partition coefficient (K) were investigated using four retention models, including Jandera's model (ABM), Neue-Kuss model (NK), linear-solvent-strength model (LSS) and quadratic-solvent-strength model (QSS). Experimental results showed that ABM model had the best fitting results for HEMWat system while NK model and QSS model had good fitting results in EBuWat system. Thus, a mathematical relationship between partition coefficient (K) and solvent strength of organic phase (ψ) could be obtained by measurement of partition coefficients of the target compounds with three different volume ratios of organic phase. At the same time, a functional map was proposed to construct to get a maneuverable region so that an optimal two-phase solvent system for separation of a target compound could be selected easily, which saved a lot of manpower for high speed countercurrent chromatographic separation. The application of this new method was declared by successful separation of two components, apigenin-6-C-β-D-xylopyranosyl-8-C-α-L-arabinopyranoside and vicenin-3, from dried leaves of Dendrobium officinale Kimura et Migo using high speed countercurrent chromatography.