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...

Keyword Year

High-performance liquid chromatography of proteins: analytical applications

K.Buchholz, B. Gödelmann, I.Molnár
Journal of Chromatography A, 238, 1, 193-202 (1982)

Keywords: HPLC, Proteins, adsorption, Trypsin, Cellulases

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http://doi.org/10.1016/S0021-9673(00)82726-0

Analysis of proteins in solution by high-performance liquid chromatography is presented with respect to structural changes in solution, adsorption processes and differentation concerning specific activities. Trypsin and cellulases were taken as examples.


Gradient Elution

L.R. Snyder
High Performance Liquid Chromatography. Advances and Perspectives, Cs. Horváth, (Academic Press, New York, 1980), vol. 1, Ch. 4

Development of the basic theory relating gradient and isocratic separations, essential to later work on DryLab I and DryLab G.


Enhancement of Retention by Ion-Pair Formation in Liquid Chromatography with Nonpolar Stationary Phases – Solvophobic Interactions Part III

Csaba Horváth, Wayne Melander, Imre Molnár, Petra Molnár
Analytical Chemistry, 49, 14, 2295-2305 (1977)

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http://doi.org/10.1021/ac50022a048

In Ion-pair reversed-phase chromatography, the retention of ionized analytes on a nonpolar bonded stationary phase is enhanced by the presence of a "hydrophobic" counterion (hetaeron) in the mobile phase. Either ion-pair formation in the mobile phase with relatively strong retention of the complex or the conversion of the stationary phase into an ion-exchanger may explain the phenomenon. Analysis of the pertinent equilibria shows that the observed hyperbolic or parabolic dependence of the capacity factors on the hetaeron concentration cannot shed light on the mechanism. The experimental data obtained for the retention of catecholamlnes by using C4-C10 alkyl sulfates and other similar hetaerons in a wide concentration range, however, could be mechanistically interpreted from the chain length dependence of the parameters for the relationship between the capacity factors and hetaeron concentration. Although the results clearly demonstrate that in the system investigated, ion-pair formation governs retention, ion-exchange mechanism can be operative under certain conditions. Changes in retention upon addition of salt to the eluent are treated both theoretically and experimentally. The effect of organic solvents on the behavior of the chromatographlc system is discussed in view of the proposed theory.


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.

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