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G Vigh

Publications and source records attributed to G Vigh.

At least 37 records · Page 2Linked to original sources
PubMed1998

Capillary electrophoretic separation of weak base enantiomers using the single-isomer heptakis-(2,3-dimethyl-6-sulfato)-beta-cyclodextrin as resolving agent and methanol as background electrolyte solvent.

The sodium salt of the single-isomer, heptakis-(2,3-dimethyl-6-sulfato)-beta-cyclodextrin (HDMS-betaCD) was used as resolving agent in the capillary electrophoretic (CE) separation of weak base enantiomers in pure methanol background electrolytes (BEs). According to the requirements of the charged resolving agent migration model of CE enantiomer separations (CHARM model), a high buffer-capacity, low pH methanolic BE was created from 25 mM phosphoric acid and 12.5 mM NaOH. In this BE, the solubility of HDMS-betaCD was as high as 50 mM, permitting the realization of very high separation selectivities and short separation times for the fully protonated weak base enantiomers.

Cyclodextrins↗
PubMed1997

Capillary electrophoretic separations of enantiomers using cyclodextrin-containing background electrolytes.

The 1996 primary literature papers which deal with the separation of enantiomers using cyclodextrins are reviewed here. Though the majority of the papers still use the neutral native cyclodextrins or the neutral derivatized cyclodextrins as resolving agents, there was a significant increase in number of separations which relied on charged cyclodextrins, both weak electrolytes and strong electrolytes, as resolving agents. Also, there was an increase in the number of papers which reported binding constants and correlated them with other physical or chemical characteristics of the analytes. Several successful minor enantiomer determinations were presented, pushing the reliable quantitation levels below 0.1%. Work continued on the simultaneous use of neutral and charged cyclodextrins to improve separation selectivity or peak resolution.

Cyclodextrins↗
PubMed1993

Displacement chromatography on cyclodextrin silicas. IV. Separation of the enantiomers of ibuprofen.

A displacement chromatographic method has been developed for the preparative separation of the enantiomers of ibuprofen using a beta-cyclodextrin silica stationary phase. The retention behavior of ibuprofen was studied in detail: the log k' vs. polar organic modifier concentration, the log k' vs. pH, the log k' vs. buffer concentration and the log k' vs. 1/T relationships; also, the alpha vs. polar organic modifier concentration, the alpha vs. pH, the alpha vs. buffer concentration and the log alpha vs. 1/T relationships have been determined in order to find the carrier solution composition which results in maximum chiral selectivity and sufficient, but not excessive solute retention (1 < k' < 30). 4-tert.-Butylcyclohexanol, a structurally similar but more retained compound than ibuprofen, was selected as displacer for the separation. Even with an alpha value as small as 1.08, good preparative chiral separations were observed both in the displacement mode and in the overloaded elution mode, up to a sample load of 0.5 mg.

Acetonitriles↗
PubMed1990

Displacement chromatography on cyclodextrin-silicas. III. Enantiomer separations.

The feasibility of preparative enantiomer separations by displacement chromatography on analytical-scale beta-cyclodextrin-silica columns, operated in the reversed-phase mode, was demonstrated using the enantiomers of mephobarbital, hexobarbital, dansylleucine, dansylvaline and dansylphenylalanine as model solutes. The method development scheme (which relies on the determination of the elution-mode retention behavior and the adsorption isotherms of the solutes and the candidate displacers) described in Parts I and II can be used to select the appropriate displacers and the conditions leading to a successful displacement chromatographic separation. The importance of the displacer (both type and concentration) to the success of the displacement chromatographic separation is demonstrated.

Amino Acids↗
PubMed1990

Separation of the enantiomeric intermediates of some platelet-activating factor analogues on a naphthylalanine-type Pirkle column.

A chiral high-performance liquid-chromatographic separation method was developed for the analysis of some glycerol-based, ether-linked platelet-activating factor precursors. Using a D-naphthylalanine-type Pirkle-column and tetrahydrofuran-hexane eluents, the retention-structure relationships were determined for a large number of glycerol ether derivatives. The derivatives leading to the highest chiral selectivity factors in the analytical separations were surveyed for their applicability in large-scale isolation of chiral synthetic intermediates.

Alanine↗
PubMed1989

Displacement chromatography on cyclodextrin-silicas. I. Separation of positional and geometrical isomers in the reversed-phase mode.

The retention behaviour of several charged and uncharged solutes on beta-cyclodextrin-silica was studied as a function of the methanol concentration, ionic strength and pH of the eluent in order to develop efficient displacement chromatographic separations for positional and geometric isomers. These retention curves were used to predict the eluent (carrier solvent) compositions that result in solute retentions in excess of k' = 10. The adsorption isotherms of several cationic detergents were determined in these carrier solutions and were found to be convex. The adsorption isotherms of several positional isomers used as test solutes were also determined in these carrier solutions. The adsorption isotherms permitted the development of efficient displacement chromatographic separations for the isomers tested. Column loadings as high as 58 mg were achieved on a regular 4.6 mm I.D. analytical-scale cyclodextrin silica columns.

Chromatography, Liquid↗
PubMed1989

Displacement chromatography on cyclodextrin-silicas. II. Separation of cis-trans isomers in the reversed-phase mode on alpha-cyclodextrin-silica.

The feasibility of preparative separations of cis-trans isomers by displacement chromatography on analytical-scale alpha-cyclodextrin-silica columns operated in the reversed-phase mode is demonstrated by using the isomers of 3-hexen-1-ol as model substrates and n-alkanols as displacers. The importance of matching the size of the cyclodextrin cavity and the solutes is shown. The crucial role of the displacer (both type and concentration) in the success of the displacement chromatographic separation is demonstrated.

Chromatography, Liquid↗
PubMed1987

Semi-preparative high-performance reversed-phase displacement chromatography of insulins.

A reversed-phase displacement chromatographic method has been developed for the purification of bovine and porcine insulin samples. Up to 500 mg of raw insulin could be purified on a Nucleosil C8 analytical column using a methanol-containing phosphate buffer carrier and a cetrimide-containing displacer. A proinsulin contamination level as low as 100 ppm in the collected fractions could be achieved.

Animals↗
PubMed1983

[Observations on pityriasis rosea patients].

In the Institute of Skin and Veneral Diseases 252 patients suffering from pityriasis rosea were treated yearly since 1970. As opposed to descriptions published so far several differences were observed. The disease occurs not only in young adults, but also in infants and in old age. It may be observed not only in certain months, but throughout the year. The disease becomes manifest more frequently in workers of larger collectives. It does not leave behind prolonged immunity, but may return after an intervall of 1-12 years with milder symptoms. The repeated incidence was 3,57 per cent. Recurrence was observed in two cases within one family. P.r. was followed by herpes zoster in 3 cases, which is indicative of increased susceptibility for viral infection. The point of attack of the supposed pathogen is the pharyngeal mucous membrane, which may explain the difficulty of isolation of the unknown virus as this region has a rich microflora.

Adolescent↗
PubMed1976

Separation of chloramphenicol intermediates by high-performance liquid chromatography on micropak-NH2 columns.

A column containing a chemically bonded phase, MicroPak-NH2, was used to seperate six components of a chloramphenicol-intermediate mixture. Two-component eluents comprising a non-hydrogen-bonding apolar solvent (cyclohexane) and a polar hydrogen-bonding solvent (dioxan, tetrahydrofuran or isopropanol) were tested. A correlation was found to exist between the values of the capacity factor (k') and the Hildebrand parameter (delta). Three-component eluents comprising cyclohexane and one of the binary mixtures dioxan-isopropanol or tetrahydrofuran-isopropanol were also studied. Optimum separation conditions with respect to analysis time, degree of resolution and detection limit were established. The system was successfully used to analyse production samples.

Chloramphenicol↗