M. Lederer

Adsorption chromatography on cellulose. IV. Separation of D- and L-tryptophan and D- and L-methyltryptophan on cellulose with aqueous solvents.

Differences in RF values between D- and L-tryptophan on cellulose paper, developed with water, were observed already in 1954 and now several variables of this separation, such as modifications to the tryptophan molecule, the temperature and salting-out have been examined. Differences were found in the mechanism of the process compared with the systems described by Yuasa et al. [Chromatographia, 21 (1986) 79], who separated amino acid enantiomers on cellulose with pyridine-ethanol-water mixtures.

Adsorption chromatography on cellulose : II. Separations of aromatic amino acids, biogenic amines, alkaloids, dyes and phenols and determination of hydrophobic constants☆

Separations of amines, phenols, alkaloids, etc., using cellulose papers or thin layers with aqueous ammonium sulphate as eluent are reported. These separations illustrate that excellent analytical separations are possible and provide data for the study of the mechanism of adsorption on cellulose from aqueous solutions.

Adsorption chromatography on cellulose : I. Salting-out chromatography of organic compounds

Abstract The adsorption on cellulose of a wide range of organic compounds from aqueous ammonium sulphate solutions was studied. The adsorption increased with increasing concentration of ammonium sulphate for all the compounds examined, and plots of their RM values against the logarithm of the activity of ammonium sulphate gave essentially parallel curves in the range from 1 M to saturated ammonium sulphate. It is concluded that the main mechanism of adsorption is a non- specific hydrophobic interaction.

Adsorption chromatography on cellulose: XI. Chiral separations with aqueous solutions of cyclodextrins as eluents

Abstract The system cellulose-aqueous α-cyclodextrin was investigated for chiral separations of tryptophan, methyltryptophans and fluorotryptophans by thin-layer and paper chromatography. The chiral effects are essentially additive (for cellulose and α-cyclodextrin), hence some large RF differences can be obtained for enantiomeric pairs. There is also a temperature effect, with an increase in ΔRF values as the temperature is decreased.

Some considerations on the “charge” on a metal ion in ion-exchange chromatography

Abstract Published work on the determination of the “charge” on an ion by means of ion-exchange equilibria is reviewed and a number of examples are discussed in which such determinations led to erroneous results. The effect of outer-sphere complexing (or ion pairing) in solution and with exchange groups is discussed.

Adsorption chromatography on cellulose VII. Chiral separations on cellulose with aqueous solvents

Abstract The chiral properties of different celluloses were examined in adsorption chromatography from aqeous solvents. Much better separations were obtained on microcrystalline cellulose than on “native” cellulose for d - and l -tryptophan and d - and l -methyltryptophan. The separation of d - and l -5-fluorotryptophan was achieved using long (40 cm) thin layers of microcrystalline cellulose.

Adsorption chromatography on cellulose: IX. Chiral separations with aqueous solvents and liquid-liquid systems

Abstract The enantiomers of substituted tryptophans were examined by thin-layer chromatography on microcrystalline cellulose. Aqueous solvents and liquid-liquid

Adsorption chromatography on cellulose XIV. Some results using aqueous solutions of soluble cyclodextrin polymers as eluents

Abstract Commercial α-, β- and γ-cyclodextrin polymers were examined for their eluent properties in adsorption chromatography on cellulose thin layers using aqueous solvents. Azo dyes were found to be eluted better by the polymers than by a solution of α-cyclodextrin. Chloroauric acid (HAuCl4) was eluted on the liquid front by polymers but not by α-cyclodextrin. No improvement could be seen in the separation of tryptophan enantiomers compared with α-cyclodextrin. α-Cyclodextrin (monomer) yields much better separations than any of the polymers. Attempts to use the polymers as non-specific desorbing agents for coloured inks were unsuccessful.

Adsorption chromatography on cellulose: VIII. The salting-out behaviour of some peptides with aromatic groups

Abstract The adsorption behaviour of some aromatic peptides on cellulose thin layers was studied. It was found that tryptophanyltyrosine and ditryptophan exhibited a “double” salting-out effect. Similarly, it was shown that for the series tyrosine, dityrosine, trityrosine and hexatyrosine the slope of the plot of RMvs. salt concentration increased with increase in the number of amino acid residues, indicating an increase in the salting-out effect.

Adsorption chromatography on cellulose XII. General effects of aqueous solutions of α-cyclodextrin as eluent

Abstract Adsorption chromatography on cellulose was examined for compounds that form complexes with cyclodextrins using aqueous solutions of α-cyclodextrin as eluent. Interesting effects were observed with methyl orange and similar diazo dyes and with aromatic nitro compounds.