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.     

Preparation of thin SnO2 layers by inorganic sol-gel process

SnO₂ sols were prepared in the following way: (1) precipitation of metastannic acid with aqueous ammonia from aqueous solutions of SnCl₄, (2) washing the precipitates with NH₄NO₃ solution and water, (3) peptization of precipitates in water, sometimes with an addition of HNO₃, at elevated temperature using mechanical stirring. In those sols, sometimes diluted with water or ethanol, substrates (glass or silica derived wafers) were dipped and withdrawn at various rates. Gel coatings were converted into crystalline SnO₂ by thermal treatment at 600°C. Coatings with thickness between 300–2000 Å were prepared.     

Small-scale thin-layer chromatography of inorganic cations on cellulose layers

Summary A method is described for the small-scale thin-layer chromatography of inorganic cations. All groups of the H₂S-systems of classical analysis can be separated on cellulose layers, using simple solvent systems. Separations obtained on Merck precoated cellulose slides are as a rule somewhat sharper than those on Avicel microcrystalline cellulose, the spots being more compact on the precoated plates.

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Dünnschicht-Chromatographie von anorganischen Kationen unter Verwendung von Celluloseschichten auf Objektträgern

Zusammenfassung Alle Gruppen des klassischen Analysenganges konnten mit Hilfe einfacher Lösungsmittelsysteme getrennt werden. Die Trennungen auf Cellulose-Fertigplatten von Merck sind im allgemeinen etwas schärfer als bei Verwendung von Avicel mikrokrist. Cellulose, weil die Hecken bei ersteren kompakter sind.

     

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.     

Separation of cephalosporins on thin silica gel layers impregnated with transition metal ions and by reversed-phase TLC

Cephalosporin antibiotics were separated on thin layer plates impregnated with transition metal ions, Mn(2+), Fe(2+), Co(2+), Ni(2+) and Cu(2+), using different concentrations. Various solvent systems were developed for the study and were used for separation of these analytes. Impregnation was observed to have an effect on hR(F) values, removed tailing of analytes and improved the resolution. The results have been discussed for each metal ion and compared, and the best conditions of separation have been identified. Activation time of thin layer plates impregnated with 0.1% FeSO(4) was found to affect both hR(F) values and resolution of cephalosporins. New solvent systems are reported for both normal phase and reversed-phase TLC.     

Study of radiation-induced polymerization of vinyl monomers adsorbed on inorganic substances. VII. Effect of pretreatment temperature of silica gel on styrene–silica gel system

To investigate the reaction mechanism of radiation-induced polymerization of styrene adsorbed on silica gel, the effect of pretreatment temperature of silica gel was studied. Preheating of silica gel was carried out at 200, 500, and 800°C. The number of silanol groups of silica gel surface decreased as preheating temperature increased. The rate of polymerization on the silica gel preheated at 500°C was faster than that at 200°C, but the polymerization rate on the silica gel preheated at 800°C was the lowest. These results suggest that rate of polymerization on the silica gel is affected by the conditions of silica gel surface such as the number of silanol groups and the pore size. At the same monomer conversion, percent grafting decreased as preheating temperature of silica gel increased. The GPC spectra of both graft polymers and homopolymers have two peaks at all preheating temperatures. The monomer conversion of low molecular weight peaks of graft polymers decreased as preheating temperature of silica gel increased. This result suggests that there is a probability that the grafting sites of low molecular weight peaks of graft polymers somehow interact with silanol groups.     

New test tools: Benzidine on cellulose and silica gel

Chromogenic reagents based on covalent and non-covalent immobilization of benzidine on cellulose and silica gels have been developed and investigated. New test tools and test methods have been elaborated for the determination of chlorine in the concentration range of 0.05–120 mg/L. Received: 6 August 1997/Revised: 13 January 1998/ Accepted: 12 February 1998