Gradienten‐Elution in der Dünnschicht‐Chromatographie

Sheet‐chromatography (thin‐layer‐ or paper‐chromatography) with gradientelution is easily performed by filling a capillary tubing solvent reservoir with effluent of a mixing battery (fig. 1a, b) and connecting the reservoir with a small solvent‐distributor laying on the sheet (fig. 1c). Hydrostatic pressure as well as suction by capillary forces regulate the solvent flow into the sheet in such a way, that all liquid leaving the reservoir is immediately picked up by the adsorbens. A simple relation therefore exists between the distance travelled by the solvent front and the volume flown out of the reservoir (fig. 10). If the composition of the mixing battery effluent is given, the solvent composition at the «immersion line» is known any time during chromatography. A micro mixing battery with up to 7 closed chambers (fig. 3) has been proved useful to produce quickly concentration gradients of liquids differing in density. The gradient‐elution is demonstrated to be reproducible on a thinlayer plate of 200 × 200 mm along the starting line (fig. 12) as well as on different thin‐layer plates (fig. 13). The method has been applied to mixtures of dyestuffs and mixtures of lipids and is able to separate e.g. squalen, O‐stearyl cholesterol, tri‐, di‐, monoglycerides, cholesterol, and polar lipids as phospholipids (fig. 14). The separation power of a gradient‐elution is highest in radial chromatography (fig. 11).