S. Pokorný

Antioxidants and stabilizers. XXXIII. Analysis of stabilizers of isotactic polypropylene: application of gel permeation chromatography

Abstract Mixtures of stabilizers, consisting of an antioxidant, light-absorber and synergist, designed to protect isotactic polypropylene against atmospheric ageing, were analysed by means of gel permeation chromatography. An acetone extract of the polymer was chromatographed on styrene—divinylbenzene gel having a molecular weight exclusion limit of 1000; the eluent was tetrahydrofuran. The values of the relative zone velocity, R, of some important stabilizers are listed and examples of quantitative analyses are discussed.

Cyclization in the reaction between diglycidylaniline and amine

SummaryThe reaction of diglycidylaniline (DGA) and N-methylaniline (NMA) was investigated by means of HPLC, and the products were identified by mass spectrometry. A number of cyclic products is formed. An eight-membered ring formed by the intramolecular reaction of the secondary amino group and the epoxy group in the DGA-aniline monoadduct is the main cyclic product. The monoadduct DGA-NMA yields a seven-membered ring by internal etherification only after the amine has been consumed.

Concentration effects in gel permeation chromatography

Abstract Viscosity phenomena were studied in columns with considerably diverse geometrical parameters. It was found that these phenomena, characterized quantitatively by statistical parameters and qualitatively by comparison of the shapes and changes in chromatograms, are identical for different geometrical arrangements. Hydrodynamic transport processes, which give rise to viscosity phenomena in chromatography of polymers, are thus general. The significance of the results ranges beyond the area of gel permeation chromatography of polymers since hydrodynamic transport processes are found every time polymer solutions pass through porous material, e.g. , in technological separation processes and the transport of macromolecules in biological media.

Concentration effects in gel permeation chromatography : V. Differential elution and viscosity phenomena

Abstract The viscosity phenomena that take place in the interstitial volume of a chromatographic column and are connected with changes in the concentration and specific viscosity of an injected polymer solution have been studied. These phenomena were also studied under conditions of differential elution when, instead of a pure solvent, solutions of the same polymer at concentrations both higher and lower than those of the injected sample were used as the mobile phase. Linear relationships were found between the elution volume and specific viscosity and between the efficiency and specific viscosity. It was also ascertained that these dependences hold under conditions of differential elution; accordingly, the absolute viscosity of the mobile phase is of minor importance for the phenomena investigated.

Gel chromatographic separation of unsaponifiable fractions in fats and oils.

Abstract Unsaponifiable compounds from fats and oils were separated by gel chromatography in tetrahydrofuran on S-832 gel with an exclusion limit of 800 molecular weight units. The elution volumes and relative zone velocities of a number of standard compounds were determined, and unsaponifiable fractions of 10 types of edible fats and oils were separated. It was demonstrated that gel chromatography combined with thin-layer chromatography is a suitable method for the effective separation of unsaponifiable fractions in fats and oils.

Concentration Effects in Size Exclusion Chromatography Under Equilibrium Stationary Conditions

Abstract In size exclusion chromatography the elution volume increases with increasing concentration of injected polymer solutions. Several particular processes contribute to this concentration effect. Under model equilibrium stationary conditions, where the phases remain immobile, it is possible to eliminate dynamic phenomena connected with the higher viscosity of polymer solution in the chromatographic zone. The only factors operative here are the effect of changes in the effective size of macromolecules in solution with a change in concentration and the effect of the varying accessible pore volume with varying concentration. The ratio of these two contributions has been investigated both theoretically and experimentally. Theoretical calculations indicated that with both phenomena operating simultaneously, the elution volumes may increase or decrease with increasing concentration according to the given experimental conditions, as a result of the coupled influence of molecular parameters of the samples u...

Gel chromatographic behaviour of bisphenols

Abstract The gel permeation chromatographic behaviour of fifty-one bisphenols was investigated with tetrahydrofuran as the eluent. In both isomeric series of compounds under investigation, the nature of the substitution of the aromatic ring has a greater influence than the volume and shape of the alkylidene bridge on the elution volume. The final effect also depends on the steric influence of substituents on the carbon atom that connects the phenolic rings and on the possibility of solvation of the phenolic groups which, in the series of 2,2′-bisphenols, is limited by the formation of intramolecular hydrogen bonds.

Curing of epoxy resins: configurational structure and reactivity of stereoisomers in the model reaction of diglycidylaniline with N-methylaniline

SummaryThe course of the model reaction of diglycidylaniline (DGA) with N-methylaniline (NMA) was followed by HPCL. By reversed phase HPCL, good separation of all reaction products and of their stereoisomers was achieved. By analysis of NMR and IR spectra, the Configurational structure of the diadduct of DGA with NMA was determined. It is demonstrated that the reactivity of the reaction components is affected by their Configurational structure.

Gel chromatographic behaviour of mononuclear aromatic hydrocarbons and phenols

Abstract The gel chromatographic behaviour of aromatic hydrocarbons and phenols during elution with tetrahydrofuran in colunns packed with styrene-divinylbenzene copolymer was investigated. From the elution volumes of 27 aromatic hydrocarbons and 80 phenols, conclusions were drawn about the effects of the types and positions of substituents and of the numbers and positions of phenolic hydroxyl groups on the elution volumes of these compounds in the system under investigation. The effects of the size of the alkyl substituents and of their positions with respect to the hydroxyl group of phenols were demonstrated, and the partial contributions of the alkyl and hydroxyl groups to the elution volumes were calculated. Chromatographic results were used for the characterization of the solvatability of phenolic molecules with tetrahydrofuran and as the basis of a discussion of problems of the steric hindrance of hydroxyl groups due to neighbouring substituents.

Comparison of Chromatographic Methods for the Analysis of Glycerol Esters

Column, thin-layer and gel chromatography have been compared as methods for the analysis of glycerol esters. It was found that gel chromatography gave much easier and faster analyses of monoglyceride emulsifiers, while at the same time providing a satisfactory distribution of fractions and giving an accuracy of determination corresponding to that of the standard method for their analysis.