Andrzej Waksmundzki

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.

Confrontation of energetic changes in sulfur/n-alkane-water and sulfur/n-alkane-vapor systems

Abstract Adsorption isotherms of n -heptane, n -octane, and n -nonane on sulfur at 30°C were determined by elution gas chromatography. From the isotherms the film pressure values and next the surface free energy γ s d for sulfur were determined. These values obtained for sulfur/ n -alkane-vapor were confronted with the film pressure and γ s d for sulfur/ n -alkane-water system, determined by electrokinetic measurements at 20°C. The γ s d value for sulfur obtained by both methods are reasonably comparable. The same may be said with respect to the literature γ s d values from contact angle measurements. Possible reasons for the observed differences in the film pressure and γ s d values are discussed. The method of elution gas chromatography for energetic studies on solids with a small specific surface seems to be useful.

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.

Effect of the support surface on the structure of the film of liquid crystalline stationary phase

Abstract It has been found that the chromatographic properties of the Chromosorb P NAW- p -butyl] p ′-hexanoylazobenzene system largely on the thickness of the liquid crystal film. Modification of the liquid crystal properties by the support surface takes place to a distance of a about 2 nm from the surface. The modified liquid crystal layer reveals a selectivity with respect to n -octane and toluene different from that of the liquid cyrstal in the bulk phase.

New Possibilities of Investigating Adsorption Phenomena by Gas Chromatography: Estimation of Adsorbent Heterogeneity from the Pressure Dependence of Retention Data

SummaryA new method is proposed for evaluating the distribution of adsorption energy on heterogeneous surfaces from the pressure-dependence of the retention volume: VN=VN(p). For this purpose Hobsons theoretical method has been adopted as most useful for testing the possibility of using gas chromatography data. Moreover, this method has been extended to a more realistic treatment of adsorption, without any loss of its basic advantages from the point of view of gas chromatography. The utility of our new method is demonstrated for two adsorption systems, using cyclohexane and cyclohexene as adsorbates, and some micro-porous silica gel as adsorbent.

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.

RF values and structure of the adsorbent in thin-layer chromatography using pure solvents as the mobile phase

Abstract The object of this paper was to investigate experimentally the reproducibility of RF values in thin-layer chromatography, and to establish the effect of the adsorbent, the molecular structure of the solute and the solvent on this reproducibility. In order to solve the problem in question, silica gel adsorbents of various micro-porous structure were used in order to show to what extent the specific surface are of the adsorbents affected the RF values. For this purpose five typical solvents were chosen which belonged to different classes according to the classification introduced by EWELL et al. and PIMENTEL AND McCLELLAN. However, for the purpose of investigating the effect of the kind of molecular structure on the RF value, substances of different molecular size, composed of one, two, or three aromatic rings, were used. The results obtained are presented as “Chromatographic spectra” and their courses are analysed. It has been concluded that the variations in RF values, including ΔRF, depend on the structure of the same type of adsorbent used, but only for some solvents. The specificity of interactions between the solute, solvent and adsorbent is responsible for the changes observed.

A simple method of plotting theoretical curves of RF as a function of pH in buffered paper chromatography

Abstract A simple method of drawing theoretical R F = f (pH) curves of organic electrolytes is described.

Properties of carbon-silica adsorbents prepared by pyrolysis of aliphatic and aromatic alcohols

SummaryA comparison of surface properties of complex carbonsilica adsorbents, obtained by pyrolysis of aliphatic and aromatic alcohols on silica gel is presented. The pyrolysis reactions of alcohols were carried out at mild conditions, above 300°C. The surface properties of these adsorbents depend upon the chemical character of the alcohol used in the pyrolysis reaction.

RF values and structure of the adsorbent in thin layer chromatography using mixed developing solvents

Abstract In the chromatographic separation of a mixture of substances a mixed mobile phase is mot frequently used in which, apart from interactions of the adsorbent with the substances separated chromatographically, a significant interaction between the molecules of the same solvent is involved. These interactions may be of various nature, one of which being hydrogen bonding. In this paper only binary solvent systems are considered, in which hydrogen bonds are (a) breaking, (b) forming, (c) breaking and forming, or (d) absent. Quinoline, isoquinoline and 3-methyl-isoquinoline, belonging to class B, according to the classification introduced by EWELL et al. and PIMENTEL AND McCLELLAN, were chosenn in order to demonstrate the effect of the solvent on the substances separated chromatographically with various silica gel adsorbents, of different specific surface area. The results obtained are presented in diagrams in which the ordinates show the RF and RM values and the abscissae the solvent composition. The investigations on the substances of the B group permit us to conclude that the RF values obtained for these substances with binary solvents vary regularly only with some solvents. These variation are especially found with systems in which broken hydrogen bonding is a predominating effect.