Forced flow rotational planar chromatography

Forced-flow development enables the mobile phase velocity to be optimized without regard to the deficiencies of a capillary controlled flow system [34,35). In rotational planar chromatography, centrifugal force, generated by spinning the sorbent layer about a central axis, is used to drive the solvent... 

A series of instruments for rotation planar chromatography have been described. These are based on the work of Hopf [61 ], more than 50 years ago, who introduced an apparatus in which the mobile pha.se was propagated by centrifugal forces. Subsequently methods have been developed by a number of researchers to control the mobile phase movement (for review, see [62 ). The separation can be performed in various types of chambers, such as in a normal chamber, a microchamber, or an ultramicrochamber. The separation takes place during constant rotation and the flow rate of the mobile phase changes throughout, i.e. the flow rate is inversely proportional to the square distance from the centre of the supply. 

Two general approaches are used for forced flow separations. Rotational planar chromatography uses centrifugal forces created by spinning the plate around a central... 

The separation efficiency of TLC is limited due to the fact that capillary forces move the mobile phase. Forced-flow techniques are an attempt to solve this problem. One approach, rotational planar chromatography, utilizes centrifugal forces and has become a widely used preparative technique. A circular plate is mounted on a centrifuge and the sample followed by the mobile phase is applied close to the center of the plate. Separated sample components can be collected when they elute from the rotating plate. 

Rotation planar chromatography (RPC), as with OPLC, is another thin-layer technique with forced eluent flow, employing a centrifugal force of a revolving rotor to move the mobile phase and separate chemical compounds. The RPC equipment can vary in chamber size, operative mode (analytical or preparative), separation type (circular, anticircular, or linear), and detection mode (off-line or online). The described technique was applied in analytical and micropreparative separation of coumarin compounds from plant extracts. 

In 2004, rotation planar chromatography (RPC), another forced-flow technique, was online coupled with... 

Nyiredy, Sz., Meszaros, S. Y., Dallenbach-Toelke, K., Nyiredy-Mikita, K., and Sticher, O. (1988b). Ultra-microchamber rotation planar chromatography (U-RPC) a new analytical and preparative forced flow method. J. Planar Chromatogr.—Mod. TLC 1 54-60. 

Forced-flow planar chromatography (FFPC) with the use of external pressure (overpressured layer chromatography, OPLC) or centrifugal force (rotation planar chromatography, RPC) can be used for off-line or on-line PLC (Mincsovics et al., 1988 Nyiredy, 1990). In off-line FFPC, the procedures after development... 

Mobile-phase velocity is higher with forced-flow development than in capillary-flow TLC. The actual flow rate is influenced by the type of chamber (rectangular or sandwich, saturated or unsaturated), the pressure and solvent viscosity (OPLC), or the rotational speed (RPC) (Nyiredy et al., 1988a). Nyiredy (1992) discussed the relation among resolution, separation distance, and time for forced-flow planar chromatography compared to capillary flow. It was stated that for separation of nonpolar compounds by FFPC on silica gel, a separation time of 1—2.5 min over a separation distance of 18 cm can be used without great loss in resolution. By contrast, longer separation times are needed for separation of polar compounds. 

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