Z. Suprynowicz

Investigations of adsorbent heterogeneity by gas chromatography : II. Evaluation of the energy distribution function

Abstract The second part is devoted to the application of gas chromatographic data in evaluating the differential distribution of adsorption energies on heterogeneous surfaces. To this purpose we have chosen Hobsons method for evaluating the energy distribution function. It is shown that the function VNVN(p), obtained directly in gas chromatography, is extremely useful in evaluating the energy distribution function.

Investigations of adsorbent heterogeneity by gas chromatography : I. Investigation of adsorption mechanism on heterogeneous surfaces

The new graphical method for investigating adsorption mechanisms on heterogeneous surfaces, developed recently by Rudzinski, Toth and Jaroniec, is applied to gas chromatographic data. It is shown that the function (∂ln p/∂ln Nt), giving the adsorption mechanism, can easily be evaluated from the function VNVN(p), obtained directly from gas chromatographic measurements. Moreover, the use of the function VN(p) in the evaluation of (∂ln p/∂ln Nt) gives a smaller error than the use of the adsorption isotherm. The utilisation of gas chromatographic data is demonstrated for four adsorption systems, obtained by using two silica gels and two adsorbates.

Separation of the isomers of some disubstituted benzenes on liquid-crystalline stationary phases in small-bore packed micro-columns

Abstract Liquid-crystalline azoxy-compounds of the type 4-[4-alkoxyphenyl)azoxy]-benzonitrile, where the alkyl group is pentyl, octyl or dodecyl, were used as stationary phases in separating isomeric disubstituted benzens. The liquid crystals were deposited on Polsorb B Naw and Polsorb B AW and placed in columns (0.8 mm I.D.). Lower HETP values were obtained with Polsorb B Naw as support. Separations of dichlorobenzenes, bromotoluenes and chlrotoluenes were achieved on a 5-m column containing 5% of the nematic pentyl derivative of the azoxy-compound concerned; xylenes wre separated on an 18-m column containing the same liquid crystal. The separations of chlorotulenes and xylens were obtained with theliquid crystal in the super-cooled state. Diethylbenzens were separated on an 18-m column containing the smectic octyl derivative of the azoxy-compound concerned.

The contribution of solution and adsorption phenomena in gas—liquid partition chromatography systems in which infinite dilution of solute may be assumed

Abstract The retention volume is assumed to consist of three parts: bulk liquid solution solid surface adsorption and liquid—gas interface adsorption. A method is presented for the quantitative evaluation of these parts by chromatography alone, when all three retention mechanisms occur.

High-density chemically bonded octadecyl phases on silica gels and their application in high-performance liquid chromatography☆

Abstract The effect of blocking of accessible surface silanol groups of silica gel support by three monofunctional octadecylsilanes having different reactive groups is investigated. The efficiency of the reaction decreases in the order N , N -dimethylaminodimethyloctadecylsilane>dimethyloctadecylmethoxysilane >dimethyloctadecylchlorosilane. The results are explained on the basis of a simplified model of the silica-gel structure by considering the type of monosilane and the effect of by-products on the reaction equilibrium. The properties of the packings are compared for the separations of caffeine and of various purine bases isolated from blood serum.

Liquid crystalline cyanoazoxybenzene alkyls carbonates as stationary phases in small-bore packed micro-columns

Abstract Three liquid crystalline cyanoazoxybenzene alkyl carbonates, with hexyl, nonyl or decyl as the alkyl radical, were investigated as stationary phases. They were deposited in various amounts on Polsorb B NAW and on Polsorb B AW and placed in 5 m X 0.8 mm I.D. columns. The retention relationship [log V′R = f (1000/T)] and column efficiency [HETP = f (V)] are connected with the properties of the liquid crystal—support system. The interactions of each of the supports with the liquid crystal differ considerably. For cyanoazoxybenzene hexyl carbonate on Polsorb B AW the efficiency obtained per metre of column length was 6830 theoretical plates. It was found that the variation of the relative retention times of the xylene isomers with column temperature is also dependent on the type of Polsorb used. The liquid crystals investigated have useful properties and can replace successfully the traditional stationary phases used for separating mixtures of various substances.

On the mechanism of support surface adsorption in gas—liquid chromatographic systems

Abstract The mechanism of support surface adsorption is investigated in gas—liquid chromatogrpahic systems with supports exhibiting strong adsorptive properties. For this purpose the characteristic adsorption isotherm for solute adsorbed on the support is evaluated, using the theoretical method developed previously by the authors. This isotherm is then analyzed on the basis of the third-order interaction theory, which allows the determination of information on the mechanism of support surface adsorption.

Study on the possibility of determining the third gas—solid virial coefficient in physical adsorption by gas chromatography

Abstract Definitions of virial coefficients used in the theory of physical adsorption of gases are discussed. A new method of evaluating the third virial coefficient is developed, based on gas chromatographic measurements. To illustrate this method, the third virial coefficient for carbon tetrachloride adsorbed on graphite was evaluated.

Comparison of mesoporous controlled-porosity glasses to silica gel as solid supports for C18 chemically bonded phases

Abstract A series of packings with chemically bonded C 18 phases has been prepared using controlled-porosity glasses with various boron contents on the surface. Based on the physicochemical and chromatographic properties, such packings are compared with those prepared from commercial silica gels. Special attention is paid to the possibility of practical application of packings prepared from mesoporous controlled-porosity glasses.

Estimation of the surface area of adsorbents from the third gas—solid virial coefficient

Abstract A new method is proposed for the estimation of the surface area of adsorbents from the second and third gas—solid virial coefficients. The method is based on a three-dimensional model of physical adsorption, and is in addition an extremely simple one. The data needed can be easily obtained by gas chromatography.