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  • 1
    ISSN: 1612-1112
    Keywords: Thin-layer chromatography ; Optimum separation ; Binary mobile phase mixtures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Up to now the optimum composition of a binary mobile phase for separation in thin-layer chromatography has been determined mainly by the method of successive trials. In this paper a simple way is presented to determine the mobile phase composition and the maximum difference in the RM values of two substances. The equation introduced has been illustrated with examples of adsorption thin-layer chromatography on magnesium silicate. Calculation of the largest difference in the RM values of two substances in relation to the composition of the binary mobile phase has been compared with the corresponding values determined experimentally. A good agreement of the obtained theoretical data and experimental values has been found.
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  • 2
    ISSN: 1612-1112
    Keywords: Thin-layer chromatography ; Adsorption ; Binary mobile phase ; Heterogeneity effects ; Chromatographic parameters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An equation describing RM values in TLC with a binary mobile phase has been derived and examined by using TLC data. Two different methods have been proposed to determine the chromatographic parameters characterizing energetic heterogeneity of the adsorption system and solute-solvent interactions. These methods differ in the estimation of the mole fractions of solvents in the surface phase. In method I an analytical equation for evaluating these mole fractions is assumeda priori. Method II utilized the excess adsorption isotherm measured for the mobile phae-adsorbent system.
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  • 3
    ISSN: 1612-1112
    Keywords: Liquid adsorption chromatography ; Molecular interactions ; Type of association
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The equation of Jaroniec was used to describe the molecular interactions in liquid adsorption chromatography with mixed mobile phases. The main object of the investigation was to demonstrate that the type of association in the bulk phase is independent of the nature of the stationary phase, and to examine the influence of the nature and number of components in the mobile phase upon the specific interactions in the system. The relationship between the type of association and the structure of the chromatographed substance was also taken into account.
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  • 4
    ISSN: 1612-1112
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Sowohl bei der Dünnschicht-Chromatographie, als auch bei der Hochdruck-Säulenchromatographie im System Flüssig-Fest werden überwiegend Gemische von Flüssigkeiten als mobile Phase eingesetzt. Um optimale Trennbedingungen in den genannten Trennsystemen finden zu können, ist die theoretische Untersuchung des Sorptionsprozesses unter den Bedingungen der Mehrkomponentenphasen notwendig. In vorliegender Arbeit wird eine Beziehung angegeben, welche den Zusammenhang zwischen RM-Werten und der Zusammensetzung von mobilen Phasen aus zwei Flüssigkeiten angibt. Die genannte Beziehung gibt auch den Zusammenhang zwischen den untersuchten Größen für den Fall an, daß die mobile Phase nur einkomponentig ist. Die Koeffizienten der Beziehung können leicht aus chromatographischen und Adsorptionsdaten ermittelt werden. Es konnte gezeigt werden, daß die Funktion RM 1,2=f(x1) in hohem Maße von der Natur des Lösungsmittelgemisches abhängt, daß heißt, ob ideale oder konformale Lösungen vorliegen. Die theoretisch berechnete Funktion wurde mit den praktisch gemessenen verglichen. Ferner wurde gezeigt, daß es möglich ist, Δ RM-Werte vorherzuberechnen. Aus diesem Grunde gelingt es, die optimalen Trennbedingungen vorauszusagen. Durch Vergleich der berechneten mit den gemessenen Funktionen gelingt es, in solchen chromatographischen Systemen für welche empirisch der Zusammenhang RM 1,2=f(x1) bekannt ist, intramolekulare Wechselwirkungsgrößen zu bestimmen.
    Abstract: Résumé Dans les processus chromatographiques de séparation des composants de mélanges, dans le cas de la chromatographie en couche mince ainsi que dans celui de la chromatographie d'adsorption en phase liquids sous haute pression, c'est très souvent un mélange de solvants, comportant de nombreux constituants, qui est utilisé comme phase mobile. Afin de choisir les conditions optimales de séparation avec les systèmes chromatographiques susdits, il est nécessaire de faire une étude théorique des processus d'adsorption dans le cas de phases mobiles formées de plusieurs constituants. Dans ce travail on a établi une équation reliant les valeurs de RM à la composition d'une phase mobile formée de deux constituants. Cette équation montre aussi la relation existant entre les valeurs de RM avec la phase mobile formée de deux constituants et les valeurs de RM dans le cas ou l'on emploit comme phases mobiles les solvants purs (phase mobile à un constituant). Les coefficients de cette équation sont mesurables par chromatographie, ainsi que par les méthodes d'adsorption. Il a été démontré que la fonctions RM 1,2=f(x1) et, par conséquent, la forme des courbes dépendent, d'une manière importante de la nature des solvants utilisés dans le cas des phases mobiles à deux constituants, par example de solutions idéales ou adaptées. On a comparé les courbes RM 1,2=f(x1) obtenues par le calcul théorique avec celles obtenues à partir des résultats de chromatographie pour les systèmes chromatographiques réels. Il a été aussi possible de déterminer théoriquement la fonction susdite et ainsi de calculer les valeurs ΔRM pour des substances données. Ainsi on peut prévoir les conditions optimales de séparation des composants de mélanges par chromatographie d'adsorption. Il est aussi possible de déterminer à l'aide de l'équation présentée dans ce mémoire, les interactions moléculaires pour les systèmes chromatographiques si les relations empiriques RM 1,2=f(x1) ont pu être déterminées. On peut le faire en comparant les formes des courbes obtenues à partir des résultats d'expérience avec celles des courbes théoriques.
    Notes: Summary Multicomponent solvent mixtures are frequently applied as the mobile phases in high pressure liquid adsorption chromatography as well as in TLC. In order to find the optimum separation conditions for these chromatographic systems it is necessary to carry out a theoretical investigation of the process of adsorption from multicomponent systems. In the present work an equation has been derived which relates the values of the RM coefficients with the composition of a two-component mobile phase. The equation also describes the relationship between the values of this coefficient and the values of the RM coefficients for the same substance but chromatographed while using pure solvents as the mobile phases. by chromatographic or adsorption methods. It has been demonstrated that the RM 1,2=f(x1) function and consequently, the shape of the curves, depend, to a considerable degree, on the type of the two-component solvent used, e.g. whether it represents an ideal or a conformal solution. The theoretical curves representing the RM 1,2=f(X1) relationship have been compared with those obtained from measurements in actual chromatographic systems. It is also possible to determine this function theoretically for a given system and thus, calculate the values of ΔRM for specified substances. Consequently, one can predict the optimum seperation conditions in adsorption chromatography. It is also possible to determine the intermolecular interactions with help of the equation derived in this paper for chromatographic systems for which the empiric RM 1,2=f(x1) relationships are known. This can be done by comparing the shape of the curves found with the shape of the theoretical curves.
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  • 5
    ISSN: 1612-1112
    Keywords: Thin-layer chromatography ; Chromatographic theory ; Adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Using adsorption TLC RM values were measured for a number of aromatic compounds on aluminium oxide and silica gels having different specific surface areas, using the following binary mobile phases: benzene+toluene, benzene+carbon tetrachloride and chloroform+carbon tetrachloride. The results are graphically presented and compared with theoretically calculated values. Generally, a good agreement was found between the calculated and measured RM values. The agreement is valid both when the RM values were calculated using experimentally (indirectly) determined partition coefficients or when the coefficients are obtained with help of Ościk's equation [cf. Roczn. Chem.34, 745 (1960) and Chromatographia4, 516 (1971)]. One can assume that in the case of systems in which strong intermolecular interactions are absent, the statically determined partition coefficients of the compounds may be used for the calculation of their RM values.
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  • 6
    ISSN: 1612-1112
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary On the basis of an equation derived it is possible to establish theoretically the RM values for a ternary mobile phase. The RM values of phenol and its derivatives, naphthalene and its derivatives and some polycyclic aromatic hydrocarbons were measured. A good agreement has been found between the calculated and the experimentally obtained RM values. Analysis of the results showed some regularities of certain values obtained in binary systems when related to the ternary mobile phase.
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  • 7
    ISSN: 1612-1112
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The paper examines the possibility of relating the RM values of a substance in a non-ideal binary solvent mixture used as the mobile phase to the adsorption characteristics of the individual solvents on the adsorbents used. The theoretically calculated $$R_{M_{1,2} } = f(\varphi _1 )$$ relationship (where ϕ1 is the volume fraction of component 1 of the binary solvent mixture in the volume phase) was compared to actual data calculated by measuring the RF values of various substances chromatographed on silica gels using thin-layer adsorption chromatography. A good agreement between the theoretical and experimental data was found.
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  • 8
    ISSN: 1612-1112
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The present paper deals with the applicability of the equation relating RM values of the solute to the composition of a two-component liquid mobile phase. Dependence of the above factors on the porosity of silica gel adsorbents, used as a stationary phase, was examined. The examinations were carried out on adsorbents with pore diameters ranging from 60 to 1000 Å. The mobile phase was a two-component solvent mixture: carbon tetrachloride — acetone. A number of aromatics were used as model solutes. The examinations showed that the porosity of silica gels when using two-component solvent mixtures which are conformal solutions as the mobile phase, has no influence on the agreement of the theoretical and experimental $$R_{M_{1,2} } = f(\varphi _1 )$$ functions. A fairly good agreement was obtained between the theoretical and experimental data.
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  • 9
    ISSN: 0935-6304
    Keywords: Thin-layer chromatography, TLC ; Liquid adsorption chromatography ; TLC with binary and ternary mobile phases ; Heterogeneity effects in TLC ; TLC data for polycyclic hydrocarbons on silica gel ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: TLC experimental data have been measured for polycyclic hydrocarbons in binary and ternary mobile phases on silica gel. These data have been interpretated using the equation discussed by us in Part 1 of this series [HRC & CC 2 (1979) 236]. The heterogeneity parameter appearing in this equation has been evaluated and compared for different ternary and binary mobile phases.
    Additional Material: 2 Ill.
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  • 10
    ISSN: 0935-6304
    Keywords: Thin-layer chromatography, TLC ; Adsorption chromatography ; TLC with mixed mobile phases ; Heterogeneity effects in adsorption chromatography ; Equations for Rm in TLC with mixed mobile phases ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thin-layer adsorption chromatography with a multicomponent mobile phase is discussed. A new equation for predicting RM-values in TLC with mixed mobile phases using the RM-ValUeS obtained for pure solvents is proposed. This equation takes into account effects of energetic heterogeneity of the adsorbent surface with regard to adsorbed molecules of solvents and solutes. Experimental verification of this equation is presented for RM-data obtained by TLC using a binary mobile phase.
    Additional Material: 10 Ill.
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