COMBINATION OF SUPERCRITICAL FLUID CHROMATOGRAPHY WITH THIN-LAYER CHROMATOGRAPHY ON A SEMIPREPARATIVE SCALE

Semi-preparative supercritical fluid chromatography (SFC) is a very valuable tool for the separation of unknown complex mixtures, as it may allow the isolation of sufficient amounts of individual constituents for H-1 and C-13 NMR spectroscopic identification. Semi-preparative SFC uses large-diameter packed columns and requires an efficient collection system. The performances of 4.6, 10 and 21 mm I.D. columns were compared and three different collection methods were tested for their efficiency: collection in pressurized stainless-steel tubes or in specially shaped glass vials, and condensation of the effluent at the starting line of a semi-preparative thin-layer chromatographic plate. The good yields that characterize the first two techniques could not be achieved with the third. The plate could, however, be developed, leading to a two-dimensional semi-preparative chromatographic separation. The spots must be localized on the plate in a non-destructive way in order to recover the samples. A general method is proposed, using berberine chloride, and also a more specific method, which allows the selective detection of certaion classes of compounds.