PubMed · 9873985
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1998-12-16. Bibliography section.. https://pubmed.ncbi.nlm.nih.gov/9873985/
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High-speed counter-current chromatography (HSCCC) was applied to the semipreparative separation and purification of puerarin and related isoflavones from a crude extract of Pueraria lobata. Analytical HSCCC was used for the preliminary selection of a suitable solvent system composed of ethyl acetate-n-butanol-water (2:1:3, v/v/v). Using the above solvent system the preparative HSCCC was successfully performed yielding six relatively pure isoflavones including puerarin from 80 mg of the crude extract in one-step separation.
Since chromatography of ions is a widely used technique in analytical chemistry a basic understanding of the retention mechanism is important. The principles of the different retention models that have been proposed are examined in this paper. The focus is on those models that are derived from the physical chemistry of charged surfaces immersed in an electrolyte solution. In the first two sections the theory for the electrical double layer and the Donnan potential are presented together with experimental results from surface and colloid chemistry. In Section 3 a comparison between stoichiometric and non-stoichiometric models is made. In this section the physical meaning of the retention factor is also examined. The Donnan model and the different double layer models developed for ion exchange chromatography of small ions are discussed in Section 4. The next section presents the corresponding models that have been developed for ion pair chromatography and compares them with the experimental findings. The theoretical modifications needed when going from small ions to ionic macromolecules are discussed in the last section and the developed models are compared with the experimental results.
The use of shear forces for the generation of the mobile phase flow in chromatographic separations is proposed. This novel chromatographic operating principle, referred to as shear-driven chromatography (SDC), completely circumvents the pressure-drop limitation of conventional pressure-driven GC and LC without affecting the operational flexibility (choice of mobile and stationary phases, possibility of solvent and/or temperature programming, etc.). In the present paper, the expression for the height equivalent to a theoretical plate in SDC in a channel with a flat rectangular cross-section is established and is used to demonstrate the large gain in analysis speed under LC, GC and supercritical fluid chromatography conditions.