Thin-layer chromatographic separation and identification of some anions on copper sulphate impregnated silica gel layers

Summary Thin-layer chromatographic behaviour of thirteen anions on plain silica gel and silica gel impregnated with copper sulphate solution has been investigated in aqueous-organic solvents containing acetone, some of which have achieved reliable and reproducible separations. The effect of copper sulphate concentration on the mobility of anions has been examined. The results obtained on plain silica gel have been compared with those obtained on copper sulphate impregnated layers. The impregnated layers dramatically change the selectivity and permit separations not possible on untreated silica. Aqueous sodium chloride-acetone (9∶1) and ammonium hydroxide-acetone (9∶1) were the most effective solvent systems for differential migration of anions. Better results in terms of clarity of detection and compactness of spots were found with HCOOH-acetone as compared to HCl-acetone. The effect of anion loading on R_F values has been investigated and identification limits on impregnated layers determined.     

Chromatographic studies of some cephalosporins on thin layers of silica gel G–zinc ferrocyanide

A simple, selective and precise thin‐layer chromatographic method has been developed for the analysis of eight cephalosporin antibiotics, namely cephadroxil, cephalexin, cefixime, cefaclor, cefpodoxime proxetil, cefuroxime axetil, cefotaxime sodium and ceftriaxone sodium. The hR_F values of these cephalosporins were investigated on silica gel G–zinc ferrocyanide layers. Mixing of zinc ferrocyanide with silica gel G resulted in a decrease in hR_F values, removal of tailing and better resolutions. The influence of silica gel G–zinc ferrocyanide ratio and mobile phases on the chromatographic behavior of cephalosporins on thin layers was investigated. Cephalosporins were selectively separated in their binary and ternary synthetic mixtures and pharmaceutical formulations. Quantitative separations of cephalosporins from their synthetic mixtures were also achieved with good recoveries (97.8–100.3%). Copyright © 2010 John Wiley & Sons, Ltd.     

Nature of the chromatographic process for inorganic substances on cellulose and silica gel thin layers

Summary The mechanism of interaction between inorganic substances and thin layers of microcrystalline cellulose and silica gel is considered. It is observed that the majority of the phenomena associated with the chromatographic behaviour of inorganic substances are not in agreement with the hypothesis of a partition mechanism on cellulose, nor with the ion-exchange mechanism on silica gel. It is concluded that the mechanism of interaction between inorganic substances and cellulose or silica gel is based on adsorption, due to electrostatic forces, primarily through hydrogen bonds between OH-groups of the adsorbent and basic ligands of inorganic complexes. The chromatographic process comprises a continual dynamic adsorption—desorption equilibrium of the complexes between the mobile phase and the stationary phase.     

TLC separation of some biologically important amino acids on pyridinium tungstoarsenate impregnated layers

Summary A satisfactory TLC separation scheme for 15 important amino acids on silica gel layers impregnated with pyridinium tungstoarsenate using isoamyl alcohol-wateracetic acid (605030) as the solvent system has been worked out. It is found that the Martin relationship is obeyed by similarly constituted amino acids. A plot of R_M vs the concentration of pyridinium ion released shows a scatter suggesting that, besides exchange properties, other factors also strongly influence the movement of amino acids.     

Sorption behaviour of some actinides on silica gel from mineral acids and alcoholic solutions

Sorption of Th, Pa, U, Np and Pu on silica gel from HNO₃, HCl and HCl−ROH solutions was investigated. Equilibrium studies indicated sorption behaviour to vary greatly with the acid used. In mixtures of HCl with different alcohols, distribution coefficints were found to depend on alcohol percentage as well as on acidity. Results were discussed and conditions for possible separations were indicated.