Performance characteristics of countercurrent separation in analysis of natural products of agricultural significance.

A standard test mix consisting of 21 commercially available natural products of agricultural significance, termed the GUESSmix, was employed to measure the countercurrent chromatography performance characteristics of a very popular quaternary solvent system family made up of hexane-ethyl acetate-methanol-water (HEMWat). The polarity range of the GUESSmix combined with the elution-extrusion countercurrent chromatography (EECCC) technique and the newly developed reciprocal symmetry (ReS) and reciprocal shifted symmetry (ReSS) plots allow liquid-liquid distribution ratios ( K D) to be plotted for every compound eluted on a scale of zero to infinity. It was demonstrated that 16 of the 21 GUESSmix compounds are found in the optimal range of resolution (0.25 < K(D) < 16) of at least one HEMWat solvent system. The HEMWat solvent systems represented by the ratios 4:6:5:5, 4:6:4:6, and 3:7:4:6 possess the most densely populated optimal ranges of resolution for this standard mix. ReS plots have been shown to reveal the symmetrical reversibility of the EECCC method in reference to K(D) = 1. This study lays the groundwork for evaluation and comparison of solvent system families proposed in the literature, as well as the creation of new solvent system families with desired performance characteristics.