Attila Felinger

University of Pecs | PTE · Department of Analytical and Environmental Chemistry

In this study, water was used as an additive in the methanol-modified carbon dioxide-based eluent for the elution of some basic organic compounds from a hybrid silica column via supercritical fluid chromatography (SFC). The experiments were applied to sulfonamides, propranolol, and other organic nitrogen compounds involving aromatic rings from diff...

The study focuses on the application range of nitrous oxide as a hold-up time marker in supercritical fluid chromatography (SFC). This compound has been suggested a decade ago to be used as unretained marker, something that the field of SFC was missing for a long time, since its beneficial properties make it an ideal candidate as hold-up time marke...

This study investigates the adsorption of methanol, water, and their mixture in a hybrid silica stationary phase with supercritical carbon dioxide as a mobile phase in supercritical fluid chromatography (SFC). The adsorption isotherms of methanol and water were determined by two dynamic methods: the elution by characteristic point (ECP) method and...

In supercritical fluid chromatography (SFC), the variation of pressure, temperature and volumetric flow-rate is most noticeable when the mobile phase contains only neat carbon dioxide. This can be explained by the compressibility of CO2 and introduces several difficulties to the work of chromatographers. The only flow parameter that is considered t...

The surface excess isotherms of methanol from carbon dioxide on reversed phase stationary phases under two different operational conditions – which can be considered subcritical and supercritical conditions depending on the molar fraction of CO2 in methanol – were determined using the minor disturbance peak method. The shapes of the surface excess...

van 't Hoff plots (logarithm of the retention factor, ln k, vs. the reciprocal of absolute temperature, 1/T) are commonly used in chromatographic studies to characterize the retention mechanisms based on the determined enthalpy (ΔH∘) and entropy (ΔS∘) change of analyte adsorption. In reversed phase liquid chromatography, the thermodynamic parameter...

A flow-reversal method combined with peak parking has been introduced recently to determine the band broadening occurring at the two respective column ends and in the bed of the packing material. Flow-reversal has a peak compression effect, therefore, the peaks observed are always narrower and more symmetrical than the peaks obtained without revers...

Uncommon retention behavior of a series of n-alkylbenzene homologues as well as the effect of different sample solvents on chromatographic efficiency were studied in supercritical fluid chromatography. After testing various columns, an alkylamide stationary phase was selected for detailed studies. The results showed that even a small amount of meth...

Background: Rheumatoid arthritis (RA) is a chronic inflammatory joint disease hallmarked by irreversible damage of cartilage and bone. Matrix metalloproteinases (MMPs) involved in connective tissue remodeling play an important role in this process. Numerous MMPs have been examined in humans and animals, but their functions are still not fully under...

(A) Cytosolic phospholipase A2 activity and (B) prostaglandin E2 levels of tibio-tarsal joint homogenates. Data are shown as mean ± S.E.M. of n = 3–7/group, ∗∗p < 0.01 vs. respective non-arthritic controls (one-way ANOVA followed by Bonferroni’s multiple comparison test).

(A) Water consumption (mL/day/mouse) and (B) percentage change of body weight (%). Data are shown as means ± S.E.M. of n = 3–13 mice/group, ∗p < 0.05 vs. respective non-arhritic control mice, ###p < 0.001 vs. tap water consuming arthritic mice (two-way ANOVA followed by Bonferroni’s multiple comparison test).

Doxycycline in high concentration (200 μg/mL), but not in lower ones inhibits in vitro MMP-9 activity in the arthritic joint homogenates. Changes of in vitro gelatinolytic activity of (A) 57–60 kDa, (B) 72 kDa, (C) 75 kDa, and (D) 92 kDa MMP isoforms in the arthritic and the non-arthritic control joint homogenates incubated with 0.2, 2, 20, and 200...

Two-dimensional correlation analysis (2DCOR) is a unique chemometric method introduced in spectroscopy which became successful in a wide range of analytical fields. It was applied in chromatography as well but has not gained wide-spread popularity. In our previous work, we introduced an alternative method, Alteration Analysis (ALA), which is built...

In the original publication of this paper, the Acknowledgements section is missing the statement below.

The impact of the column length (5, 10, and 15 cm) and packing mode (constant pressure and constant flow rate up to 15,000 psi) on the radial and axial heterogeneities of 3.0 mm i.d. research prototype columns packed with the same batch of 2.4 μm BEH-C18 particles was investigated by the flow reversal technique. The data were gathered for a non-ret...

It may happen under the conditions employed that enantiomers interconvert to each other. In this case, obviously, the kinetics of the process is to be examined. When enantiomers dynamically interconvert to each other during the separation process, a plateau is observed between the adjacent peaks (so-called Batman peak appears). The peak shape depen...

The mass-transfer properties of a core-shell packing material with 1.6 μm particle diameter, and that of a fully porous packing material with 1.7 μm particle diameter were investigated and compared. The first absolute and the second central moments of the peaks of the homologous series of alkylbenzenes, over a wide range of mobile phase velocities...

The biosorption of phenol on non-living lyophilized mycelial pellets of Phanerochaete chrysosporium cultivated in liquid medium of various compositions was studied in batch biosorption system. The fungal cell surfaces were characterized by FTIR spectroscopy and specific surface charge determination. The sorption kinetics and equilibrium were evalua...

The thermodynamics of the retention mechanism of resorcinarene-based cavitands in RPLC as well as the nature of the binding sites have been studied recently. In the present study, the influence of pressure on the retention of the cyclic tetramers on alkylsilyl and polar-embedded C8 and C18 stationary phases is investigated using aqueous methanol mo...

Kinetic theories of liquid chromatography play a key role in evaluating the performance of stationary phases. The conventionally used plate height equations and the band broadening occurring in the different areas of liquid chromatography are accounted for by kinetic models. In this chapter, the most important macroscopic (lumped kinetic, lumped po...

Hydrophilic interaction liquid chromatography (HILIC) has become in the last years a leading technique for the separation of small and large polar molecules. This chapter begins with a discussion about the most relevant characteristics of this chromatographic mode that makes HILIC a complementary and, in some cases, alternative technique to the mor...

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...

A numerical method was introduced for the estimation of the surface heterogeneity below an adsorbed multilayer of the analyte. The calculation procedure 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...

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 kinetic performance of five chromatographic columns designed for fast liquid chromatography with different column packing materials – including fully porous (2.0 and 1.9 μm particles), core-shell (2.6 μm particles) or monolithic packings – with identical column dimensions (2.1 × 50 mm) were tested. Since the tested monolithic column showed syst...

Two-dimensional correlation analysis (2DCOR) is a well-established method in chemometrics to extract information hidden in a series of measurements. That field is still thriving on its every possible corner, with new tests, perturbations, calculations, and samples. There is still an unexploited way, however, where 2DCOR can expand quite significant...

The adsorption capacities of alginate, chitosan and immobilized Spirulina platensis-maxima cells were studied in a continuous packed-bed column, under dynamic condition. The composition of alginate and chitosan beads was optimized. Various operating conditions were applied; the effect of flow rate, column height and initial metal ion concentration...

Cavitands are cavity-shaped cyclic oligomers and they can create host–guest interactions with various analytes, therefore they have applications in supramolecular chemistry, nanoscale reactions, chromatographic separations, drug encapsulation and delivery, biochemistry. The investigation of the chromatographic behavior of large molecules, such as r...

Unifloral honeys have a high commercial value and should undergo a strict quality control before marketing. This study aimed at determining floral origin, polyphenolic compounds and antioxidant activity in 7 samples marketed as lavender and thyme honeys. The samples were subjected to pollen analysis to confirm their botanical origin. Coupled chromat...

In this study, a microscopic probabilistic model of chromatography that establishes a conceptual link between single-molecule dynamics observation at liquid-solid interfaces and chromatographic experiments is described. This model is based on the discrete Lévy representation of stochastic processes and has the great advantage that it can be directl...

Thymus species belonging to the Lamiaceae family are popular spices and contain volatile oils as main chemical constituent. Different Thymus species (Thymus vulgaris, Thymus serpyllum, Thymus pulegioides, and Thymus glabrescens) were collected from the Medicinal Plant Garden of the University of Medicine and Pharmacy in Târgu. Mureş (Romania). Vola...

Millions of people use mobile phones (MP) while drinking coffee or other caffeine containing beverages. Little is known about the potential combined effects of MP irradiation and caffeine on cognitive functions. Here we investigated whether caffeine intake and concurrent exposure to Universal Mobile Telecommunications System (UMTS) MP-like irradiat...

The family Solanaceae includes several melliferous plants, which tend to produce copious amounts of nectar. Floral nectar is a chemically complex aqueous solution, dominated by sugars, but minor components such as amino acids, proteins, flavonoids and alkaloids are present as well. This study aimed at analysing the protein and alkaloid profile of t...

Thymus pannonicus All., T. glabrescens Willd., T. pulegioides L., T. praecox Opiz and Thymus serpyllum L., indigenous collective species in the Hungarian flora, were involved in our studies. Content and composition of essential oils and polyphenolic fractions were examined in grown populations, originating from different wild habitats, at the Exper...

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...

The understanding of the retention behavior of large molecules is an area of interest in liquid chromatography. Resorcinarene-based cavitands are cavity-shaped cyclic oligomers that can create host-guest interactions. We have investigated the chromatographic behavior of two types of cyclic tetramers as analytes in high-performance liquid chromatogr...

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...

This study aimed at systematic and historic collecting of ethnomedicinal plants in 3 villages in Transylvania, part of Romania in 2011-2013, and detecting polyphenol compounds of the selected Ononis arvensis and Rhinanthus serotinus by LC-MS. The aerial part of Ononis arvensis was mentioned for diarrhea, liver and stomach disorders, and Rhinanthus...

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 ge...

With the need for high-frequency data acquisition, the influence of the data acquisition rate on the quality of the digitized signal is often discussed and also misinterpreted. In this study we show that undersampling of the signal, i.e. low data acquisition rate will not cause band broadening. Users of modern instrumentation and authors are freque...

The biosorption of heavy metals by dried Chlorella vulgaris and Spirulina platensis-Spirulina maxima cells was studied under various experimental conditions. The effects of biosorbent dosage, pH, adsorption time, temperature, initial metal concentration on the biosorption were examined. A biosorption process can be divided into two parts: the first...

The mass-transfer properties of three superficially-porous packing materials, with 2.6 and 3.6μm particle and 1.9, 2.6, and 3.2μm 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 an...

We investigate the impact of polydispersity of the sample molecules on the separation process and on the efficiency of size-exclusion chromatography. Polydispersity was integrated into the molecular (stochastic) model of chromatography; the characteristic function, the band profile and the most important moments of the elution profiles were calcula...

This special issue of Chromatographia contains papers presented at the 9th Balaton Symposium on High-Performance Separation Methods, which was held in Siófok, Hungary on September 4–6, 2013. The Balaton Symposia are organized by the Hungarian Society for Separation Sciences (HSSS).The first Balaton Conference was organized in 1995 and since then th...

Bergenia species (Saxifragaceae) are important sources of herbal medicines in Asia, mainly in Russia. Various plant parts are valued for their antibacterial, anti-inflammatory, antioxidant sand adaptogenic effect, and used for the dissolution of kidney and bladder stones. In this study a rapid reversed phase liquid chromatography (RP-HPLC) method h...

The adsorption capacities of six biosorbents (Pseudomonas aeruginosa, Pseudomonas fluorescens, Escherichia coli, Chlorella vulgaris, and Spirulina platensis) for Zn(II) ions under batch condition have been studied. The optimum pH range was found to be 5.0-6.0. The amount of adsorbed Zn(II) ions were between 18 and 128 mg/g. Characterization of bios...

In this work, the influence of the width of particle size distribution (PSD) on chromatographic efficiency is studied. The PSD is described by lognormal distribution. A theoretical framework is developed in order to calculate heights equivalent to a theoretical plate in case of different PSDs. Our calculations demonstrate and verify that wide parti...

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 i...

Non-equilibrium crystallization was simulated on a two dimensional square lattice. Several clusters were grown simultaneously by using the model of diffusion limited aggregation. The growing process was reversible, i.e. dissolution of particles from the boundary of any cluster was made possible. The rate of growth and dissolution was determined by...

The adsorption isotherms of both naproxen enantiomers were measured on a (R,R)-Whelk-O1 chiral adsorbent from a mobile phase made of liquid carbon dioxide and methanol, using frontal analysis. These isotherms were used to model the competitive adsorption behavior of a racemic mixture of naproxen enantiomers. Their overloaded elution band profiles w...

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 si...

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 chromato...

Kinetic theories of liquid chromatography play a key role in evaluating the performance of stationary phases. The conventionally used plate-height equations and the band broadening occurring in different areas of liquid chromatography are accounted for by kinetic models. In this chapter, the most important macroscopic (lumped-kinetic, lumped-pore,...

Hydrophilic interaction liquid chromatography (HILIC) has become in the last years a leading technique for the separation of small and large polar molecules. This chapter begins with a discussion about the most relevant characteristics of HILIC mode that makes it a complementary and, in some cases, alternative technique to the more traditional reve...

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 succes...

n-Hexane, chloroform, ethyl acetate and 50% ethanol in water extracts prepared from the air-dried flowering parts of Lythrum salicaria L. were tested for in vitro pharmacological properties on Guinea-pig ileum, which is suitable for detecting a whole range of neuronal and smooth muscle effects. UHPLC-MS was used to evaluate polyphenol components of...

The volatile composition of eight varietal wines Vranec, Merlot, Cabernet Sauvignon, Temjanika and Chardonnay from the Republic of Macedonia, and Portugieser, Kékfrankos and Tokaji Aszú from Hungary has been characterized by means of gas chromatography/mass spectrometry technique. The wine volatile compounds were extracted in dichloromethane, and t...

Methods are proposed to calculate surface excess isotherms and to use them to derive adsorption isotherms in liquid chromatography. The consequences of these methods are discussed. The excess isotherm of isopropyl alcohol from its aqueous solutions on a C18 adsorbent was obtained using the minor disturbance method. The slope of the inflection tange...

In this study the kinetics and equilibrium of phenol biosorption were studied from aqueous solution using batch technique at an initial pH of 5.5. The biosorption was studied on Ca-alginate beads, on non-living mycelial pellets of Phanerochaete chrysosporium immobilized on Ca-alginate, and on free fungal biomass. Ph. chrysosporium was grown in a li...

The goal of the study was to investigate the retention mechanism of selected fungicides in hydrophilic interaction liquid chromatography (HILIC) and per aqueous liquid chromatography (PALC). Chromatographic measurements were made on four physicochemically diversified HILIC columns, which were evaluated for the analysis of nine biologically active c...

The effect of the coverage density and the activity of the unreacted silanol groups of the non-endcapped octadecyl bonded phase on the adsorption properties were investigated. The adsorption of two polar low molecular weight compounds with weak acidic (phenol) and with basic (aniline) character was measured. Adsorption data were acquired by frontal...

Hyoscyamine (atropine) and scopolamine are the predominant tropane alkaloids in the Datura genus, occurring in all plant organs. The assessment of the alkaloid content of various plant parts is essential from the viewpoint of medical use, but also as a potential risk of toxicity for humans and animals. Therefore, a reliable method for the determina...

A study was conducted to investigate artifacts in liquid-phase separations-system, solvent, and impurity peaks. Solvent peaks were observed when nonselective detectors were used. It was also possible to observe solvent peaks on a chromatogram recorded by a specific detector. Changes in the refractive index of an organic modifier mixture with water...

The optimization of preparative separations has been in the focus of interest for decades. The optimization of isocratic and gradient overloaded elution, and the optimization of displacement chromatography makes possible a comprehensive comparison of the performance of the different modes of chromatography. The importance of the retention factor, t...

A number of models in chromatography have analytical solutions in the Laplace or Fourier domain. Often, the moments of the Laplace domain solutions are calculated to characterize the peak shape. Nonlinear fitting in the Fourier domain can be performed to exploit the entire peak shape rather than the moments only. Curve fitting in the Fourier domain...

Polyphenolic compounds represent a wide group of phytochemicals, including well-known subgroups of phenolic acids, flavonoids, natural dyes, lignans etc., which are produced by plants. These natural bioactive compounds possess a variety of beneficial effects including antioxidant and anticarcinogenic activities, protection against coronary diseases...

The stochastic or microscopic model of chromatography has been applied to determine overall mass-transfer coefficients from peak shapes recorded in reversed-phase liquid chromatography. The stochastic model of chromatography describes the separation process at the molecular level by probabilistic terms. This microscopic model is rather straightforw...

The adsorption isotherms of acetonitrile, ethanol, 2-propanol, and THF were measured using frontal analysis on six columns packed with octadecyl RP stationary phase. The effect of the bonding density of the end-capped octadecyl bonded phase on the adsorption properties was measured. Adsorption isotherm data were collected from aqueous solutions of...

The adsorption isotherms of phenol were acquired by frontal analysis on six different reversed phase adsorbents from five different organic solvent solutions. The end-capped octadecyl columns only differed in the bonding density of the C(18) ligands. The inverse method was used to confirm the estimated isotherm parameters derived from the frontal e...

The recently developed pellicular packing materials show high efficiency and have attracted great interest. The improved mass-transfer kinetics of the core-shell particles is due to the shorter diffusion path of the molecules within the stationary phase. In this study we show how the diffusion time of the molecules visiting the stationary phase dep...

The adsorption behavior of proline under hydrophilic interaction chromatography conditions was investigated from six aqueous solutions of acetonitrile. Proline adsorption isotherms were recorded at each mobile phase composition by frontal analysis and inverse method. The BET model was found to be the best choice to describe the nonlinear behavior o...

A detailed, molecular-level description of the sorption mechanism in reversed-phase liquid chromatography is of great interest to analytical chemists. For this purpose, solvent adsorption in the octadecyl stationary bonded phase was investigated. Preferential adsorption of solvents from an acetonitrile-water and methanol-water mobile phase was meas...

The present study aimed at determining selected alkaloid components in the nectar of Datura species, to elucidate whether the alkaloid content of the floral nectar can lead to intoxication. A simple and rapid liquid chromatography coupled with electrospray mass spectrometry analysis was developed for the quantitative determination of atropine and s...

Adsorption of acetonitrile and methanol was measured on non-endcapped and endcapped octadecyl stationary phases. The results enabled us to characterize the effect of end-capping on the adsorption of the organic modifiers. Our results clearly demonstrate how the end-capping groups modify the chromatographic properties of adsorbents. Differences betw...

The characterization of mass-transfer processes in a chromatographic column during a separation process is essential, since the influence of the mass-transfer kinetics on the shape of the chromatographic band profiles and on the efficiency of the separation is crucial. Several sources of mass transfer in a chromatographic bed have been identified a...

The potential role of androgen metabolism as co-factors in the development of carcinoma endometrii was investigated. The urinary concentration of 23 androgen, progesterone and corticoid metabolites was quantitatively determined by gas chromatography-mass spectrometry with selected ion-monitoring. We obtained 24-h urine samples from 13 patients with...

The excess adsorption isotherms of methanol, 2-propanol, acetonitrile, and tetrahydrofuran from water were measured on five silica-based packing materials by the minor disturbance method. The adsorbed amount of solvents was calculated per silica gel surface and per modeled surface of bonded phase which seem to give more correct data. Columns used i...

For the correct description of a chromatographic process, the determination of mass-transfer kinetics in the column is required because the influence of the mass-transfer kinetics on the shape of chromatographic band profiles is crucial. Several sources of mass transfer in a chromatographic bed have been identified and studied: the axial dispersion...

The excess adsorption isotherms of organic modifiers (methanol and acetonitrile) from water on chemically bonded stationary phases were studied, using seven different packed columns with different organic ligand lengths from C4 to C30. Isotherms were measured using the minor disturbance method. Excess isotherms can give useful information about the...