1973 Volume 22 Issue 4 Pages 389-393
The relations between the discontinuous gradient front and the composition of polar and non-polar solvents in two-component solvent systems in thin-layer (TLC) and dry column chromatography (DCC) have been investigated.
For the experiments with TLC and DCC, silica gel and mixtures of the following non-polar and polar solvents were used. Non-polar solvents : benzene, cyclohexane and carbon tetrachloride. Polar solvents : alcohols (methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 2-propanol, 2-butanol, 2methyl-1-propanol and 3-methyl-1-butanol), carboxylic acids (acetic acid, propionic acid and butylic acid), ketones (acetone, methylethyl ketone, methylpropyl ketone, methylisopropyl ketone and methylisobutyl ketone), esters (methyl acetate, ethyl acetate, propyl acetate and butyl acetate) and bases (diethylamine, triethylamine, tributylamine and pyridine). In the TLC, a BN-chamber was used as the developing chamber, and the running distance was 12 cm from the lower side of the layer and in the DCC, a column of inner diameter 1 cm and length 12 cm was used. The, β-front formed by chromatographic demixing was detected by the fluorescence under ultra-violet ray (3600 Å) and color of the components (e. g. pigments, and 2, 4-dinitrophenyl derivatives of amines and amino acids) concentrated on the β-front.
In both TLC and DCC, the linear relationship based on the adsorption isotherm of Freundlich was observed between the migration rate of the demixing line (K β value) and the concentration (mole percent) of the polar component. The range of the concentration in which this relationship hold was about 5 30 mole percent except for the following solvent systems (Fig. 15) : tributylamine systems, propyl acetate systems and butyl acetate systems (120 mole percent) ; acetic acid-cyclohexane or carbon tetrachloride system and methanol systems (2060 mole percent). The following tendencies with regard to K β values were found within the above mentioned concentration range if the concentrations were the same. The K β values of normal- and iso-alcohol systems were nearly the same (Table I). The K β values in most of the systems which contained the same polar components decreased in the order of benzene systems, carbon tetrachloride systems and cyclohexane systems (Table II). It was also found that the K β values in each series of non-polar solvent systems which contained those solvents having the same functional group, increased with the increase in the molecular weight of the polar solvent (Fig. 1, 2, 4, 5).
