Optimising resolution for a preparative separation of Chinese herbal medicine using a surrogate model sample system.

J Chromatogr A. 2009 May 3; Ye H, Ignatova S, Peng A, Chen L, Sutherland IThis paper builds on previous modelling research with short single layer columns to develop rapid methods for optimising high-performance counter-current chromatography at constant stationary phase retention. Benzyl alcohol and p-cresol are used as model compounds to rapidly optimise first flow and then rotational speed operating conditions at a preparative scale with long columns for a given phase system using a Dynamic Extractions Midi-DE centrifuge. The transfer to a high value extract such as the crude ethanol extract of Chinese herbal medicine Millettia pachycarpa Benth. is then demonstrated and validated using the same phase system. The results show that constant stationary phase modelling of flow and speed with long multilayer columns works well as a cheap, quick and effective method of optimising operating conditions for the chosen phase system-hexane-ethyl acetate-methanol-water (1:0.8:1:0.6, v/v). Optimum conditions for resolution were a flow of 20ml/min and speed of 1200rpm, but for throughput were 80ml/min at the same speed. The results show that 80ml/min gave the best throughputs for tephrosin (518mg/h), pyranoisoflavone (47.2mg/h) and dehydrodeguelin (10.4mg/h), whereas for deguelin (100.5mg/h), the best flow rate was 40ml/min.