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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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.


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

The applicability of core-shell phases in preparative separations was studied by a modeling approach. The preparative separations were optimized for two compounds having bi-Langmuir isotherms. The differential mass balance equation of chromatography was solved by the Rouchon algorithm. The results show that as the size of the core increases, larger particles can be used in separations, resulting in higher applicable flow rates, shorter cycle times. Due to the decreasing volume of porous layer, the loadability of the column dropped significantly. As a result, the productivity and economy of the separation decreases. It is shown that if it is possible to optimize the size of stationary phase particles for the given separation task, the use of core-shell phases are not beneficial. The use of core-shell phases proved to be advantageous when the goal is to build preparative column for general purposes (e.g. for purification of different products) in small scale separations. © 2015 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.


Lambert N.,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: 2015

We have studied the chromatographic behavior of the homologous series of alkylbenzenes (ranging from octylbenzene to octadecylbenzene) on the same C18 reversed-phase column in supercritical fluid chromatography (SFC) and reversed phase liquid chromatography (RPLC) at various experimental conditions, such as different eluent compositions, flow-rates, and mobile phase densities.The first and the second moments of the peaks were used to estimate the overall mass-transfer processes in both chromatographic modes using the stochastic model of chromatography.The results confirm that in SFC - as the density of the mobile phase is influenced by the flow-rate - there is a broader variation of mass-transfer properties than in liquid chromatography.As expected, the optimum mobile phase velocity is higher in SFC, but there is no real difference in the minimum value of plate height, i.e. in the optimum efficiency. © 2015 Elsevier B.V.


PubMed | University of Pécs and MTA PTE Molecular Interactions in Separation Science Research Group
Type: Journal Article | Journal: Journal of mass spectrometry : JMS | Year: 2016

We established a new reversed phase-high performance liquid chromatography method combined with electrospray ionization quadrupole time-of-flight tandem mass spectrometry for the simultaneous determination and structural characterization of different lipid A types in bacteria (Escherichia coli O111, Salmonella adelaide O35 and Proteus morganii O34) showing serological cross-reactivity. The complex lipid A mixtures (obtained by simple extraction and acid hydrolysis of the outer membrane lipopolysaccharides) were separated and detected without phosphate derivatization. Several previously unidentified ions were detected, which differed in the number and type of acyl chains and number of phosphate groups. In several cases, we observed the different retention of isobaric lipid A species, which had different secondary fatty acyl distribution at the C2 or the C3 sites. The fragmentation of the various, C4 monophosphorylated lipid A species in deprotonated forms provided structural assignment for each component. Fragmentation pathways of the tri-acylated, tetra-acylated, penta-acylated, hexa-acylated and hepta-acylated lipid A components and of the lipid A partial structures are suggested. As standards, the hexa-acylated ion at m/z 1716 with the E.coli-type acyl distribution and the hepta-acylated ion at m/z 1954 with the Salmonella-type acyl distribution were used. The results confirmed the presence of multiple forms of lipid A in all strains analyzed. In addition, the negative-ion mode MS permitted efficient detection for non-phosphorylated lipid A components, too. Copyright 2016 John Wiley & Sons, Ltd.

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