Two-dimensional chromatography, notwithstanding its undoubted advantages from a theoretical point of view, is the least studied separation technique owing to the difficulty in interpretating the experimental results. The technique has two main drawbacks: the possibility of analysing only one sample on one sheet without the simultaneous spotting of test compounds' and the difficult interpretation of a twodimensional chromatogram on the basis of RF values obtained by one-dimensional developments. Even the quantitative analysis of two-dimensional chromatograms is difficult, as the spots are not arranged in vertical strips but occupy the whole layer. Nevertheless two-dimensional chromatography can separate very complex mixtures which are difficult to resolve by means of other techniques'.
This paper describes a method which allows the use of chromatographic data in order to calculate similarity criteria without having quantitative data. The problem of sample classification on the basis of chromatographic results is generally carried out by means of pattern recognition techniques using the quantitative data from gas chromatography or high-performance liquid chromatography3. EXPERIMENTAL Flavonoids aglycones of elm and iris leaves were examined. The crushed leaves (1 g) were treated with 25 ml of boiling hydrochloric acid for 30 min. The flavonoids were extracted with 10 ml of ethyl acetate, which was evaporated to dryness under vacuum. The residue was dissolved in 2 ml of methanol and 2 ~1 of this solution were spotted on Sil Crs-50 plates (Macherey, Nagel & Co.) and eluted in the first direction with n-hexane-ethyl acetate-acetic acid (72:27:1) and in the second direction with 1 M acetic acid in 50% methanol. The spots were sprayed with a 1% methanolic solution of ethanolamine diphenylborate and a 5% ethanolic solution of polyethylene glycol. The spots were observed under UV light (360 nm). Under these conditions the flavonoids give fluorescent spots of different colours. The spots were characterized by their positions on the layer by means of two coordinates, obtained by dividing the