Progress in forced-flow planar chromatography

This paper summarizes progress in forced-flow planar chromatography (FFPC) and demonstrates the importance of the different techniques like rotation planar chromatography (RPC), overpressured-layer chromatography (OPLC), and electro-planar chromatography (EPC). Special attention is paid to a novel analytical FFPC method in which continuous development and continuous evaporation of the mobile phase from the end of the chromatographic plate ensure forced-flow development. A simple, but powerful preparative forced-flow technique is also reported; in this technique hydrostatic pressure is used to increase mobile-phase velocity. Parallel- and serially coupled layers open up new vistas for the analysis of a large number of samples (up to 216) for high throughput screening and for the analysis of very complex matrices. The special features of fully off-line and fully on-line RPC, OPLC, and EPC are compared in a table. New detection methods—on-line coupling of OPLC with radiodetection and on-line OPLC–MS—are also discussed. The role of a new spraying device for post-chromatographic chemical detection and for biological detection is also discussed. Some applications, relating to different classes of substances, are given to demonstrate the versatility of the various FFPC techniques.     

New insight into the biosynthesis of flavanolignans in the white-flowered variant of Silybum marianum

It has been demonstrated that besides the known flavanolignan constituents of the white-flowered variant of Silybum marianum, (-)-silandrin A (3a) and (-)-isosilandrin A (4a); their trans-benzodioxane diastereomers, (-)-silandrin B (3b) and (-)-isosilandrin B (4b), are also produced by the plant. Moreover, the isolation of their cis-benzodioxane diastereomers, (-)-isocisilandrin (5) and cisilandrin (6), confirm that the previously proposed biosynthetic pathway involving a nonselective O-beta coupling is correct.     

Investigation of Thermal Degradation of PVC in the Solid State

The thermal degradation of PVC powders and the inhibition of this process by cadmium laurate was investigated by the measurement of discoloration, diffuse reflectance spectra, and the quantity of hydrochloric acid formed. Kinetic analysis of the data obtained by us previously showed that both the data of color measurements and those of diffuse reflectance spectra may be used conveniently for the calculation of the number of double bonds formed during the degradation.     

Preparative medium pressure liquid chromatographic (MPLC) and semipreparative HPLC separation of furocoumarin isomers

Chromatographia - Preparative medium pressure liquid chromatography and semi-preparative high performance liquid chromatography on silica were employed for the isolation of eight furocoumarin...     

Planar chromatographic method development using the PRISMA optimization system and flow charts

This study presents a modern planar chromatographic method-development procedure, based on the "PRISMA" optimization system, in which the optimum separation is achieved systematically and the structures and properties of the substances to be separated are not known. The procedure consists of three stages. In the first of these the basic conditions the stationary phase, vapor phase, and individual solvents are selected with a TLC procedure (generally in nonsaturated chromatographic chambers). In the second stage, the optimum combination of the selected solvents is determined with the PRISMA model. The third part of the procedure includes the selection of the development mode (circular, linear, or anticircular); the selection of an appropriate forced-flow chromatographic technique (over-pressured layer chromatography or rotation planar chromatography) with high-performance thin-layer chromatographic plates; the transfer of the optimized mobile phase to the various analytical, planar, or column preparative liquid chromatographic techniques; and the selection of the operating conditions. For practical reasons, the optimization process is presented with the help of flow charts.     

Determination of neutral cannabinoids in hemp samples by overpressured-layer chromatography

Summary The overpressured-layer chromatographic separation of neutral cannabinaids (Δ⁹ -tetrahydro-cannabinol, cannabidiol, cannabinol, cannabigerol and cannabichromene) has been achieved on amino HPTLC plates with dichloromethane as mobile phase. By use of bidirectional development up to 30 samples can be analysed on a 10 cm×20 cm plate within 4 min. Evaluation was performed by slit-scanning densitometry at 200 nm. System-suitability data confirm the applicability of the method. Presented at Balaton Symposium 01 on High-Performance Separation Methods, Siófok, Hungary, September 2–4, 2001