RF values and structure of the adsorbent in thin-layer chromatography using pure solvents as the mobile phase

Abstract

The object of this paper was to investigate experimentally the reproducibility of R F values in thin-layer chromatography, and to establish the effect of the adsorbent, the molecular structure of the solute and the solvent on this reproducibility. In order to solve the problem in question, silica gel adsorbents of various micro-porous structure were used in order to show to what extent the specific surface are of the adsorbents affected the R F values. For this purpose five typical solvents were chosen which belonged to different classes according to the classification introduced by EWELL et al. and PIMENTEL AND McCLELLAN. However, for the purpose of investigating the effect of the kind of molecular structure on the R F value, substances of different molecular size, composed of one, two, or three aromatic rings, were used. The results obtained are presented as “Chromatographic spectra” and their courses are analysed. It has been concluded that the variations in R F values, including Δ R F , depend on the structure of the same type of adsorbent used, but only for some solvents. The specificity of interactions between the solute, solvent and adsorbent is responsible for the changes observed.