Comparison of optical in-situ scanning of conventional and high-performance thin-layer chromatograms

Conventional TLC, linear and circular HPTLC are compared by using In-situ reflectance measurements. Chromatographic resolution, time requirement and reproducibility of quantitative scanning of the different TLC methods are investigated by means of three separation problems: benzodiazepines, corticosteroids, polycyclic aromatic hydrocarbons. In all three application examples, which were chosen without prejudice, the circular developing mode with subsequent quantitative scanning showed certain advantages over the corresponding linear HPTLC techniques. These were in the case of

• Benzodiazepines: Better reproducibility of quantitative assessment.
• Corticosteroids: Better resolution and slightly better quantitative reproducibility.
• Polycyclic aromatic hydrocarbons: Chromatography considerably faster.