Optimization of chromatographic systems for the high-performance thin-layer chromatography of flavonoids

To characterize the retention and selectivity of separations of 23 flavonoi ds (aglycones and glycosides) relationships between R-F and modifier concen tration were determined for silica and diol adsorbents (with mixtures of et hyl acetate and methanol as mobile phases), for cyanopropyl silica (with mi xtures of ethyl acetate and dichloromethane as mobile phases), for aminopro pyl silica (with mixtures of ethyl acetate, methanal and water as mobile ph ases) and for octadecyl silica (with mixtures of methanol and water as mobi le phases). Owing to large polarity differences between aglycones and glyco sides, these groups of compounds cannot be separated other than by use of r eversed-phase systems, for which the selectivity is lower. It follows from correlation plots of R-F1 against R-F2 that for some pairs of adsorbents (e .g. silica and diol) selectivity differences are small; for others the poin ts in the plot a re widely dispersed, indicating selectivity differences. T he chemometric database obtained can be used to choose optimum chromatograp hic systems for the separation of given sets of flavonoids and for planning gradient elution programs for separation of flavonoid aglycones and glycos ides in a single TLC experiment.