MTA PTE Molecular Interactions in Separation Science Research Group

Pécs, Hungary

MTA PTE Molecular Interactions in Separation Science Research Group

Pécs, Hungary
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Barto E.,University of Pécs | Felinger A.,University of Pécs | Felinger A.,MTA PTE Molecular Interactions in Separation Science Research Group | Jandera P.,University of Pardubice
Journal of Chromatography A | Year: 2017

In the present work, the adsorption of water was investigated in aqueous normal-phase liquid chromatography on Cogent Silica C and Cogent Phenyl hydride stationary phases at different temperatures by frontal analysis – using coulometric Karl Fischer titration – to compare the temperature dependence of adsorption of water from aqueous acetonitrile. The Cogent Silica-C and Cogent Phenyl Hydride columns have a silicon hydride surface (silica hydride) with less than 2% free silanol group; therefore, they do not have a strong association with water. The adsorption behavior of water on the mentioned stationary phases was modeled by Langmuir isotherm. The preferentially adsorbed water was expressed in terms of a hypothetical monomolecular water layer equivalent in the inner pores. The uptake of water slightly depends on the temperature. The adsorbed water may fill four to eight percent of the pore volume over the studied temperature range, which approximately corresponds to the equivalent of 0.24–0.68 water layer coverage of the adsorbent surface. The phenyl hydride stationary phase shows decreased water uptake in comparison to the Silica C stationary phase. © 2017 Elsevier B.V.


Horvath K.,University of Pannonia | Vajda P.,MTA PTE Molecular Interactions in Separation Science Research Group | Felinger A.,MTA PTE Molecular Interactions in Separation Science Research Group | Felinger A.,University of Pécs
Journal of Chromatography A | Year: 2017

A numerical method was introduced for the estimation of the surface heterogeneity below an adsorbed multilayer of the analyte. The calculation procedure is based on the raw adsorption isotherm data points obtained by frontal analysis experiments. To permit the mapping of the nature of the analyte-surface interaction, a numerical procedure was used to pre-estimate the adsorbate-adsorbate interactions occurring during the adsorption process. The surface heterogeneity estimation was carried out using the affinity-energy distribution calculations with assuming local BET isotherm. In the local BET isotherm the pre-estimated adsorbate-adsorbate interaction constant was used, and the surface heterogeneity was described. After the test of the numerical method with benchmark isotherms, the algorithm was tested on several experimental isotherms. The isotherms were measured using phenol as test molecule on reversed phase adsorbents, with different surface coverage of the octadecyl ligands. The surface of the non-end-capped stationary phases showed detectable heterogeneity, while the surface end-capped phases were found to be homogeneous. © 2017 Elsevier B.V.


Simon J.,MTA PTE Molecular Interactions in Separation Science Research Group | Felinger A.,MTA PTE Molecular Interactions in Separation Science Research Group | Felinger A.,University of Pécs
Chemometrics and Intelligent Laboratory Systems | Year: 2017

Alteration analysis (ALA) has been recently introduced to expand the two-dimensional correlation analysis (2DCOR) into further dimensions. 2DCOR is unable to work with 3D data arrays composed from a series of 2D measurements, but ALA has the advantage that it does not increase (multiply) the dimensions of the original data sets. Thus, it can easily be applied to more complex systems. ALA, however, does not work only with 3D arrays, but with matrices as well. In this study we present a comparison of the two methods. ALA has a different mathematical background, indicating that it has different properties. Therefore, some drawbacks are inevitable, however, ALA has a number of advantages over 2DCOR. While 2DCOR emphasises the correlation between the changes, ALA focuses on individual changes and provides more detailed information about them. Furthermore, we demonstrate that the connection between these changes can also be described with ALA. Besides, ALA simplifies the visual representation, because instead of two 2D maps (2DCOR) the information is shown on a single linear graph. Therefore, ALA is not only an extension, but it can be an alternative to 2DCOR. © 2017 Elsevier B.V.


Horvath K.,University of Pannonia | Sepsey A.,MTA PTE Molecular Interactions in Separation Science Research Group | Hajos P.,University of Pannonia
Journal of Chromatography A | Year: 2015

An algorithm was developed for the minimization of consumption of organic solvent in comprehensive two-dimensional liquid chromatography (2DLC). It was shown that one can reach higher peak capacities only by using more eluent. The equilibration volume of the second dimension, however, did not affect the solvent consumption significantly. Calculations confirmed that the same target peak capacity could be achieved by consuming significantly different volume of organic modifier depending on the number of fractions analyzed in the second dimension suggesting that 2D separations can be optimized for eluent consumption. It was shown that minimization of eluent usage requires the use of small and high efficient columns in the second dimension. A simple equation was derived for the calculation of the optimal number of collected fractions from the first dimension that allowed the minimization of eluent usage, cost and environmental impact of comprehensive 2DLC separations. © 2014 Elsevier B.V.


Vajda P.,University of Pécs | Felinger A.,University of Pécs | Felinger A.,MTA PTE Molecular Interactions in Separation Science Research Group
Journal of Chromatography A | Year: 2014

Multilayer adsorption is often observed in liquid chromatography. The most frequently employed model for multilayer adsorption is the BET isotherm equation. In this study we introduce an interpretation of multilayer adsorption measured on liquid chromatographic stationary phases based on the fractal theory. The fractal BET isotherm model was successfully used to determine the apparent fractal dimension of the adsorbent surface. The nonlinear fitting of the fractal BET equation gives us the estimation of the adsorption equilibrium constants and the monolayer saturation capacity of the adsorbent as well. In our experiments, aniline and proline were used as test molecules on reversed phase and normal phase columns, respectively. Our results suggest an apparent fractal dimension 2.88-2.99 in the case of reversed phase adsorbents, in the contrast with a bare silica column with a fractal dimension of 2.54. © 2013 The Authors.


Bacskay I.,University of Pécs | Sepsey A.,MTA PTE Molecular Interactions in Separation Science Research Group | Felinger A.,University of Pécs | Felinger A.,MTA PTE Molecular Interactions in Separation Science Research Group
Journal of Chromatography A | Year: 2014

The mesopore structure (pore size and its distribution) for the first and second generations of silica-based monolithic columns was determined by inverse size-exclusion chromatography. The effect of pore size distribution was considered via the molecular theory of size-exclusion chromatography. The molecular theory of chromatography allows taking into account the kinetics of the pore ingress and egress processes, the heterogeneity of the pore sizes and polymer polydispersity. Besides, the mesopore structure, the characteristic domain sizes of the macropores present in the first and second generations of silica-based monolithic columns were also characterized. © 2014 Elsevier B.V.


Lambert N.,MTA PTE Molecular Interactions in Separation Science Research Group | Kiss I.,University of Pécs | Felinger A.,MTA PTE Molecular Interactions in Separation Science Research Group | Felinger A.,University of Pécs
Journal of Chromatography A | Year: 2014

The mass-transfer properties of three superficially-porous packing materials, with 2.6 and 3.6. μm particle and 1.9, 2.6, and 3.2. μm inner core diameter, respectively, were investigated and compared with those of fully porous packings with similar particle properties. Several sources of band spreading in the chromatographic bed have been identified and studied according to the general rate model of chromatography. Besides the axial dispersion in the stream of the mobile phase, and the external mass transfer resistance, the intraparticle diffusion was studied in depth. The first absolute and the second central moments of the peaks of human insulin, over a wide range of mobile phase velocities were measured and used for the calculation of the mass-transfer coefficients. The experimental data were also analyzed using the stochastic or molecular dynamic model of Giddings and Eyring. The dissimilarities of the mass-transfer observed in the different columns were identified and evaluated. © 2014 Elsevier B.V.


Sepsey A.,MTA PTE Molecular Interactions in Separation Science Research Group | Bacskay I.,University of Pécs | Felinger A.,MTA PTE Molecular Interactions in Separation Science Research Group | Felinger A.,University of Pécs
Journal of Chromatography A | Year: 2014

Chromatographic processes can conveniently be modeled at a microscopic level using the molecular theory of chromatography. This molecular or microscopic theory is completely general; therefore it can be used for any chromatographic process such as adsorption, partition, ion-exchange or size exclusion chromatography. The molecular theory of chromatography allows taking into account the kinetics of the pore ingress and egress processes, the heterogeneity of the pore sizes and polymer polydispersion. In this work, we assume that the pore size in the stationary phase of chromatographic columns is governed by a wide lognormal distribution. This property is integrated into the molecular model of size exclusion chromatography and the moments of the elution profiles were calculated for several kinds of pore structure. Our results demonstrate that wide pore size distributions have strong influence on the retention properties (retention time, peak width, and peak shape) of macromolecules. The novel model allows us to estimate the real pore size distribution of commonly used HPLC stationary phases, and the effect of this distribution on the size exclusion process. © 2014 Elsevier B.V.


Bacskay I.,University of Pécs | Sepsey A.,MTA PTE Molecular Interactions in Separation Science Research Group | Felinger A.,University of Pécs | Felinger A.,MTA PTE Molecular Interactions in Separation Science Research Group
Journal of Chromatography A | Year: 2014

Stationary phases in liquid chromatography exhibit quite different pore structures. Whereas most of the fully porous packing materials possess a narrow pore size distribution, core-shell particles are usually of rather wide pore size distribution. Recently a novel theory of size exclusion chromatography was introduced to model the effect of pore size distribution. The molecular theory of chromatography allows taking into account the kinetics of the pore ingress and egress processes, the heterogeneity of the pore sizes and polymer polydispersity as well. The novel model was applied to inverse size exclusion chromatography data. In this study, we have determined the actual pore size distribution of a number of HPLC stationary phases. Our results agree well with the results obtained with the model introduced by Knox and Scott. © 2014 Elsevier B.V.


Simon J.,University of Pécs | Felinger A.,University of Pécs | Felinger A.,MTA PTE Molecular Interactions in Separation Science Research Group
Journal of Chromatography A | Year: 2015

Two-dimensional (2D) correlation analysis is a well-established tool in spectroscopy. Despite its versatility in various measurement systems, 2D correlation has not yet become popular in separation science. 2D correlation is seldom used in chromatography; only a few a studies can be found on this topic and most of those publications report about gel chromatography. In the present study, 2D correlation analysis is applied to chromatograms. In this study, a simple method is built for studying the similarities and dissimilarities between a number of chromatograms. We present the applicability of the method by two examples, where the repeatability and reproducibility of the analytical and nonlinear measurements in HPLC are evaluated and demonstrated. In order to validate the results of 2D correlation analysis, they are compared to principal component analysis (PCA). We confirm the equivalence in the interpretation of the results obtained with the two methods of calculation. The results confirm that 2D correlation can be a successful chemometric tool in chromatography. © 2015 Elsevier B.V.

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