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- Author or Editor: Grzegorz Jóźwiak x
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A horizontal DS chamber for TLC has been adapted for planar electrochromatography in closed system. A test dye mixture was separated on pre-wetted RP-8 and RP-18 chromatographic plates with acetonitrile-buffer as mobile phase. A potential of 2 kV was applied to a 10-cm plate to create the electric field. Two modes of electrochromatogram development were applied — in open and closed (pressurized) systems. The disadvantages of the open system — evaporation of the mobile phase from the plate and excessive flow of mobile phase to the surface of the adsorbent layer during development — were eliminated by use of the closed system. Highly reproducible retention was achieved during planar electrochromatography in the closed system when the adsorbent layer of the plate was pre-wetted and equilibrated with a solution of the mobile phase. Examples are presented of electrochromatograms obtained from the test dye mixture under different operating conditions. Separation efficiency in planar electrochromatography was higher than in conventional HPTLC.
By use of pH 6.0 acetate buffer a mixture of Chelidonium majus L. alkaloids has been separated, on a classical silica column, into two groups, tertiary and quaternary alkaloids. The relationships between R F and the concentration of methanol in the acetate buffer suggested it was possible, by gradient elution in which the concentration of methanol in the pH 6.0 aqueous acetate buffer was increased, to separate the quaternary alkaloids further into fractions containing 2 or 3 alkaloids. These fractions were then separated by micropreparative zonal thin-layer chromatography. Sanguinarine and chelerithrine of high purity were obtained.
A strategy has been established for preparative-layer chromatography of the alkaloid fraction from Fumaria officinalis . An extract obtained by maceration and percolation of the milled plant material with 0.5 m aqueous acetic acid was re-dissolved in methanol and fractionated by column chromatography on alumina. Two of the fractions obtained, containing medium polarity alkaloids and strongly polar alkaloids, respectively, were used in the preparative-layer chromatography experiments. Preliminary work focused on investigation of overloading, methods of sampling, effect of layer thickness on band resolution, and the effect of derivatization on the location of separated bands. Another objective of the work was to investigate the use of unidimensional multiple development (UMD) and incremental multiple development (IMD) for resolution of the alkaloids found in Fumaria officinalis extracts.
Commercially available hop pellets of different origins were extracted by use of ethanol and water, chromatographed on silica layers by use of nonaqueous eluents, chemically derivatized and observed in ultraviolet (UV) light for the localization of component bands. The plates were developed in optimized systems, and direct bioautographic method by use of Bacillus subtilis and Escherichia coli strains was applied for the examination of the antimicrobial activities of hop components. The method enables for the identification of bactericidal/bacteriostatic components in the extracts of different polarities and shows differences in the composition of extracts from various varieties from an antimicrobial point of view.
Plant extracts from Datura innoxia Mill. contain tropane alkaloids which are pharmacologically active, and compounds used in medicine are isolated industrially from the plant. Control of the composition and content of these alkaloids is, therefore, an important task. Thin-layer chromatography is an effective method for analysis of these compounds, because they are difficult to detection with UV light. In the work discussed in this paper separation of closely related alkaloids was achieved by two-dimensional TLC in optimized NP and RP systems by use of multiphase plates. The work enabled identification of tropane alkaloids present in plant extracts. Normal-phase separation on silica layers was optimized for quantitative analysis of the alkaloids scopolamine and tropine and the sum of atropine and homatropine.
