Literature

DryLab draws on the philosophy described in the three most famous Solvophobic Theory papers IIIIII of Csaba Horváth, which were developed in the years 1975-1977 at Yale University (see also literature by Dr. Imre Molnár). Read more about the Fundamentals of DryLab...

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Rapid separation of urinary acids by high-performance liquid chromatography

Imre Molnár, Csaba Horváth
Jornal of Chromatography, 143, 391-400 (1977)

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http://doi.org/10.1016/S0378-4347(00)80985-8

0ver a hundred acidic urinary constituents were separated within 30 min by using 5-µm octadecylsilica columns and gradient elution with increasing acetonitrile concentration in dilute aqueous phosphoric acid solution at 70°. The column effluent was monitored with a UV detector at 280 nm or with a fluorescence detector at 260 nm excitation and 340 nm emission wavelengths. The high sensitivity and speed of analysis, the excellent reproducibility and adequate resolution obtained suggest that this technique may be useful to obtain metabolic profiles in routine clinical work.


Separation of Amino Acids and Peptides on Non-polar Stationary Phases by High-Performance Liquid Chromatography

Imre Molnár, Csaba Horváth
Journal of Chromatography, 142, 623-640 (1977)

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http://doi.org/10.1016/S0021-9673(01)92073-4

Microparticulate non-polar stationary phases, such as octadecyl-silica offer a rapid and efficient means for the separation of peptides and amino acids by high-performance liquid chromatography. Retention is attributed to hydrophobic interaction between the solutes and the hydrocarbonaceous functions covalently bound to the stationary phase surface. Consequently the species are eluted in the order of increasing hydrophobicity. Various peptide mixtures were analyzed by using gradient elution with increasing acetonitrile concentration in the eluent and monitoring the column effluent at 200 or 210 nm with an UV detector. The separation of angiotensins and enzymic digest of polypeptides illustrates the speed of the method which can be used to assay the purity of peptide hormones such as α-melanotropin and gramicidin or to analyze the composition of reaction mixtures involving peptides. The efficiency of the method is superior to that obtained on the conventionally used ion-exchanger columns, except for hydrophilic amino acids and peptides that are poorly retarded. Nevertheless, with a suitable ionic surfactant in the mobile phase, non-polar stationary phases can be used for the separation of these species as well.


Liquid Chromatography of Ionogenic Substances with Nonpolar Stationary Phases – Solvophobic Interactions Part II

Csaba Horváth, Wayne Melander, Imre Molnár
Analytical Chemistry, 49, 1, 142-154 (1977)

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http://doi.org/10.1021/ac50009a044

The effect of solute ionization on the retention of weak acids, bases, and ampholytes on octadecylsilica was investigated both theoretically and experimentally. The retention was attributed to a reversible association of the stationary phase. A phenomenological treatment of the corresponding equilibria was developed for various types of ionogenic substances. The energetics of the association process was analyzed in a rigorous fashion in the light of the solvophobic theory and a semi-empirical extension of the Debye-Hückel theory to high ionic strength. The predicted effect of solute ionization on the capacity factors was substantiated by experimental data. The observed dependence of the capacity factors on the ionic strength of the eluent and the hydrophobic surface of the solute molecules showed good agreement with the theory. The advantages of the technique in the separation of biological substances are illustrated.


Rapid Analysis of Peptide Mixtures by High Performance Liquid Chromatography With Nonpolar Stationary Phases

I. Molnár, Cs. Horváth
Peptides (Proc. 5th Am. Peptide Symp.), M. Goodman, J. Meienhofer, (Wiley, New York, 1977), 48-51

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Charcoal, a nonpolar sorbent, had been widely used for the separation of peptides1 before the advent of ion-exchange chromatography. Recent developments in high performance liquid chromatography revived the interest in the use of nonpolar stationary phases for the separation of biological substances by “reversed phase” chromatography, which employs columns packed with 5 or 10µm porous silica particles having hydrocarbonaceous functions covalently bound to the surface.

This report illustrates the potential of this type of chromatography for the rapid analysis of minute quantities of peptide mixtures. The results suggest that octadecyl-silica columns can be used for fast separation of a wide variety of peptides. By monitoring the column effluent with a UV-detector at 200 nm, the sample components can be analyzed at the subnanomole level without the formation of UV absorbing or fluorescent derivatives.


Solvophobic Interactions in Liquid Chromatography with Nonpolar Stationary Phases – Solvophobic Interactions Part I

Csaba Horváth, Wayne Melander, Imre Molnár
Journal of Chromatography , 125, 129-156 (1976)

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http://doi.org/10.1016/S0021-9673(00)93816-0

Solute interaction with nonpolar stationary phases in liquid chromatography is examined on the basis of the solvophobic theory. The chromatographic process is viewed as a reversible association of the solute with the hydrocarbonaceous ligands of bonded phases. A detailed analysis of the effect of the solvent on this process yields an expression for the capacity factor with essentially no adjustable constants. The theory satisfactorily accounts for the factors affecting solute retention under a wide range of experimental conditions. It makes possible the characterization of the solvophobic (eluent) strength of mixed solvents having different composition and the evaluation of the various solvophobic forces representing incremental values of the logarithm of the capacity factor. The wide applicability of nonpolar stationary phases (reversed phases) in liquid chromatography is demonstrated by the rapid separation of biogenic acids and bases on octadecylsilica columns with neat aqueous elements.

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