RETENTION BEHAVIOR OF CLOSELY RELATED COUMARINS IN THIN-LAYER CHROMATOGRAPHIC PREASSAYS FOR HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY ACCORDING TO THE PRISMA MODEL

The retention behaviour of fourteen closely related coumarins in normal-phase thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC) was studied with the aim of testing the suitability of TLC as a preassay for HPLC when the optimization of the mobile phase has been carried out according to the "PRISMA" system. The retention (retardation) in TLC and HPLC was measured at 37 and 13 selective points, respectively. The retention behaviour at different solvent strengths was also examined. Capacity factors (k') and separation factors (alpha) were calculated to study the retention behaviour in the two systems. Two- and three-dimensional evaluations of k' against selectivity points showed similar retention behaviour for the coumarins in TLC and HPLC. According to quadratic regression, k' showed a dependency on the change in solvent strength. Similar behaviour of alpha values for TLC and for HPLC was demonstrated in three-dimensional evaluations.