Katarzyna Adamska

Inverse gas chromatography as a source of physiochemical data

Inverse gas chromatography (IGC) is presented as a useful method for the examination of physicochemical properties of various materials. The advantages of IGC are presented. However, the uncertainties and sources of possible errors are also indicated and discussed.

The increase of apatite layer formation by the poly(3-hydroxybutyrate) surface modification of hydroxyapatite and β-tricalcium phosphate

The aim of this study was the surface modification of hydroxyapatite and β-tricalcium phosphate by poly(3-hydroxybutyrate) grafting and characterization of modificates. The bioactivity examination was carried out by the determination to grow an apatite layer on modified materials during incubation in simulated body fluid at 37°C. The additional issue taken up in this paper was to investigate the influence of fluid replacement. The process of the surface modification of biomaterials was evaluated by means of infrared and Raman spectroscopy. Formation of the apatite layer was assessed by means of scanning electron microscopy and confirmed by energy dispersive, Raman and Fourier transformed infrared spectroscopy. During exposure in simulated body fluid, the variation of the zeta potential, pH measurement and relative weight was monitored. Examination of scanning electron microscopy micrographs suggests that modification of hydroxyapatite and β-tricalcium phosphate by poly(3-hydroxybutyrate) significantly increases apatite layer formation. Raman spectroscopy evaluation revealed that the formation of the apatite layer was more significant in the case of hydroxyapatite modificate, when compared to the β-tricalcium phosphate modificate. Both modificates were characterized by stable pH, close to the natural pH of human body fluids. Furthermore, we have shown that a weekly changed, simulated body fluid solution increases apatite layer formation.

The solubility parameter for biomedical polymers-Application of inverse gas chromatography.

The solubility parameter seems to be a useful tool for thermodynamic characterisation of different materials. The solubility parameter concept can be used to predict sufficient miscibility or solubility between a solvent and a polymer, as well as components of co-polymer matrix in composite biomaterials. The values of solubility parameter were determined for polycaprolactone (PCL), polylactic acid (PLA) and polyethylene glycol (PEG) by using different procedures and experimental data, collected by means of inverse gas chromatography.

Characterization of ceramic hydroxyapatite surface by inverse liquid chromatography in aquatic systems.

The novel approach for hydroxyapatite (HA) surface characterization was proposed. The main aim of this investigation was to estimate surface properties of HA as a biomaterial in real system i.e. in simulated body fluid (SBF). One of the method, which might be used to reflect the influence of liquid environment on sorption properties of material being surrounded by this liquid, is called inverse liquid chromatography (ILC). The lowercase letters of LFER equation (e, s, a, b, v) served for this characterization. The sorption abilities of examined material were also estimated for two different aqueous mobile phases: deionized water and water solution of 0.1M Na2HPO4. It enabled to observe the change in physiochemical properties of surface, considered in Abraham model, dependence on ions concentration in the mobile phase. Moreover pH of every aquatic solution, normally about 7, was adjusted to 5.5 and 9 to observe the influence of hydrogen and hydroxyl ions concentration on HA sorption properties.

Solubility parameter used to predict the effectiveness of monolithic in-needle extraction (MINE) device for the direct analysis of liquid samples.

The sorbent/eluent systems combined from three macroporous poly(styrene-divinylbenzene) (PS-DVB) monoliths and four solvents as eluents were used for the extraction of phenol, 4-chlorophenol and p-benzochinon from water samples. Monolithic in-needle extraction (MINE) devices were used in the preparation of a series of test water samples for chromatographic analysis. The extraction of phenolic compounds from water samples was carried out by pumping liquid samples through the MINE device. Solubility parameter concept was applied for estimation of effectiveness of MINE. Solubility parameters for (PS-DVB) monoliths were determined according to Small, considering different molar fraction of the monomers used for synthesis. Effectiveness of these systems was estimated according to difference of solubility parameter value in analyte/sorbent, sorbent/eluent, analyte/eluent pairs. The procedure enabling easy prediction of, e.g. the strength of the interactions between the analyte and sorbent, eluent efficiency or the extraction efficiency in MINE system was proposed.

Determination of Hansen Solubility Parameters by Means of Gas-Solid Inverse Gas Chromatography

The determination of Hansen Solubility Parameters (HSP) from inverse gas chromatographic (IGC) data for a group of nano-materials and modified nano-materials is presented and discussed. The solubility parameter concept is applied in many industries to explain the different properties of the various components in a formulation. Knowledge of the solubility parameter data for different components is important for predicting the magnitude of the interaction between the formulation components and the future stability of the product. Solubility parameter data are also useful in the description and interpretation of different phenomena occurring between materials such as their miscibility, compatibility or adsorption. The inverse gas chromatography method is widely used for the characterization of polymers and polymer blends, surfactants, biopolymers, solid food and petroleum pitches. The method involves placing the investigated material (stationary phase) in a column and then characterizing it using volatile probes with known properties (test solutes) which are carried by a mobile phase. The solubility parameter called the Hildebrand solubility parameter or the Hildebrand parameter is only applied for regular solutions. The so-called Hansen solubility parameter (HSP) is an extension of the Hildebrand solubility parameter to polar and hydrogen-bonding systems. Hansen assumed that the cohesive energy can be considered as the sum of the contributions from dispersive (Ed), polar (Ep) and hydrogen-bonding (Eh) interactions: –Ecoh = –Ed – Ep – Eh; and that the total solubility parameter (δT) may be expressed as δT2 = δd2 + δp2 + δ2h, where δp, δp and δh denote the dispersive, polar and hydrogen-bonding contribution, respectively. The estimation of HSP from IGC data for a group of nano-materials and modified nano-materials is presented and discussed here.

Characterisation of hydroxyapatite surface modified by poly(ethylene glycol) and poly(hydroxyethyl methacrylate) grafting

Hydroxyapatite (HA) has many applications in medicine as a biocompatible and bioactive biomaterial. Numerous studies have shown that modification of the HA surface can improve its biological and chemical properties. However, little is known about the surface properties of modified materials. In this paper the influence of organic polymers: polyethylene glycol (PEG) and polyhydroxyethyl methacrylate (pHEMA) on the surface properties and surface chemistry of hydroxyapatite (HA) is presented. The surface properties of modified HA were characterised by the FT-IR, XPS, BET, and zeta potential measurements. Specific surface area was determined by BET. Infrared and XPS spectra confirmed the presence of PEG and pHEMA on the surface of HA. The BET N2 adsorption revealed slight changes in the HA surface chemistry after grafting modification. The surface chemical properties of the HA were considered to be based on the zeta potential. The decrease in zeta potential results in the increasing stability of the modified material and also in the reduction of bacterial adhesion. The reaction for surface modification of HA is proposed and described.

Characterization of surface of trifluorophenylketoiminepropyl stationary phase coated porous layer open tubular columns

A series of 3 fluorinated adsorbents were prepared by bonding 4,4,4-trifluoro-1-phenyl-1,3-ketoiminepropyl silane onto 5μm Nucleosil silica. The first one contained sole fluoroketoimine groups, while the other two adsorbents were derivatives of the first one with copper(II) chloride and copper(II) acetylacetonate bound through the fluoroketoimine groups. A description of syntheses of these adsorbents is given and the course of each stage of the syntheses is characterized by elemental analysis, surface area determination, UV-vis, EPR, ICP-OES, IR, (29)Si NMR, (13)C NMR and thermogravimetric analysis. For the columns coated with the adsorbents obtained the donor-acceptor character of the adsorption layer was established and the enthalpy of adsorption was determined for a selected group of hydrocarbons. The evenness of capillary column walls coating and mechanical stability of the stationary phases was evaluated on the basis of the flow restriction factor and SEM images. Efficiency of the columns obtained and their comparison with commercial counterparts are presented.

Properties of materials as determined by inverse gas chromatography

Properties of materials as determined by inverse gas chromatography The application of inverse gas chromatography (IGC) in the determination of the physicochemical properties of various materials is presented and discussed. The special attention is focused on the determination of solubility parameters.

The Physicochemical Characteristics of Prosthetic Materials and Their Influence on Their Clinical Properties

The use of elastic materials favours degradation of their surface. The period of their clinical usefulness is then shortened, and their further utilisation in the oral cavity may have the reverse effect. The surface properties of such material as well as the influence of the humidity on their surface are very important as they determine the prosthetic materials behavior in the mouth. The surface of such material should be resistant to water. Inverse gas chromatography is an accurate, sensitive technique for studying surface properties. Thanks to using a unique equipment specially designed for IGC technique, Surface Energy Analyzer, it was possible to characterize the surface at 0 and 80% of humidity. Our results show that increased humidity does not affect surface properties of studied prosthetic materials. Their ability to dispersive and specific interactions change in very limited degree. IGC experiment was also applied for the estimation of Hansen solubility parameters that indicate ability of a material to dispersive, polar, and hydrogen-bonding interactions. Relation between the surface characteristics and practical use of soft lining materials with implications for their clinical usefulness is also discussed.