Adam Voelkel

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.

Theoretical and experimental methods of determination of the breakthrough volume of SPE sorbents.

Solid-phase extraction is one of the most popular sample preparation methods. The selection of the appropriate extraction system is an important stage in the elaboration of analytical procedure. In this case, the knowledge of the interactions between isolated compounds, sorbent and elution solvents seems to be important. The extraction ability of sorbents in the SPE bed depends also on: (i) the bed capacity; (ii) the volume of sample loaded, (iii) the nature and volumes of conditioning solvents and eluents. One of the important parameters is the breakthrough volume, which determines the maximum volume of water sample which can be introduced into the sorbent. In this work two methods of determination of the breakthrough volumes are presented: experimental method with frontal analysis, and theoretical method with computational applications. Both procedures were used for the characterization of nine polymeric sorbents based on divinylbenzene copolymers. Comparison of results allows to choose the computational procedure of breakthrough volume determination as the easier one and less time consuming.

Examination of surfaces of solid polymers by inverse gas chromatography: 2. Acid-base properties

Abstract The application of inverse gas chromatography (i.g.c.) for the examination of surface properties of solid materials is discussed. A group of analogous poly(dimethacrylate)s differing only by the presence and type of the heteroatom in the ester group and two reference polymers were characterized by means of this method. In this paper the dispersive properties expressed by υsd and C1 PDS determined at various temperatures (50–70°C) are presented and discussed. It was found that chemically similar polymers may be differentiated in terms of their dispersive parameters. The values of υsd and C1 PDS depend on the temperature of the i.g.c. measurement, which is determined by the relative temperature gradient. During heat treatment at 80°C and 160°C, the surfaces of the polymers undergo significant modification depending on the annealing atmosphere (helium or air). This modification is revealed by changes in the dispersive parameters and variations in the relative temperature gradients. The relationship between υsd and C1 PDS is linear, but the plots are unique for each polymer.

Increments of some polarity parameters for polyoxyethylene glycol dialkyl ethers and for some of their sulphur analogues

Abstract Gas-liquid chromatography was used to determine the polarity of pure model polyoxyethylene glycol dialkyl ethers and of some their sulphur analogues. The polarity parameters were correlated with the surfactant structure and increments for characteristic groups were determined. These values can be used to estimate the polarity of surfactants using only their formulae.

Identification of organic extractables from commercial resin-modified glass-ionomers using HPLC-MS.

Elution of organic compounds from resin-based dental fillings during their application in the human mouth environment may have a potential impact on the human health. Ethanol, water and other solvents very often present in the human mouth have the ability to penetrate dental fillings placed in the human tooth. Penetration of liquids into the tooth may lead to the liberation of unreacted dental filling ingredients or their degradation products. Determination of these compounds is necessary for better knowledge from possible harmful effects caused by dental fillings. The aim of this study was the isolation and identification of compounds released from resin-modified glass-ionomer cements (RMGICs), resin-based dental materials applied in dentistry. Compounds were extracted from fillings by using four solvents (40% ethanol, water, 1% acetic acid and artificial saliva). Liquid samples containing eluted compounds were then extracted, evaporated and analyzed by using of HPLC-MS (high-performance liquid chromatography-mass spectrometry) and HPLC-DAD (high-performance liquid chromatography-diode array detection) techniques. Almost thirty components (monomers and additives) of RMGICs were identified. The main identified extractables were: Bis-GMA (bisphenol A glycidyl dimethacrylate), Bis-EMA (ethoxylated bisphenol A dimethacrylate), UDMA (urethane dimethacrylate), TEGDMA (triethylene glycol dimethacrylate), HEMA (2-hydroxyethyl methacrylate) as monomers and diphenyliodonium chloride, camphorquinone (initiators), BHA (inhibitor), 4-(dimethylamino) ethyl benzoate (co-initiator) as additives.

Characterisation of mineral oil–polyester,mineral oil–poly-α-olefin mixtures by inverse gas chromatography

Poly-α-olefins and polyesters are the base stocks for the production of synthetic oils, and after mixing with mineral oils for semi-synthetic oils. Their behaviour at the temperatures found in a car engine at work (around 140 °C) is very important. The authors propose the use of an inverse gas chromatography (IGC) technique for qualification of their mixing properties. Information on the basic parameters for SN-200 oil (H-6), poly-α-olefin (PAO-6), ester (DB-51) and their mixtures H-6–PAO-6, H-6–DB-51 was obtained from standard, normalised methods. All examined base oils and their mixtures were placed in gas chromatographic columns and act as liquid stationary phases in the chromatographic process. The Flory–Huggins parameter χ∞12 was calculated from the retention data (IGC) for selected test solutes. For the mixtures H-6–PAO-6, H-6–DB-51 the values of Flory–Huggins parameter χ∞1(2,3) were calculated. The interactions between components of investigated mixtures were expressed by the Flory–Huggins interaction parameter χ∞23.

Polarity of polyoxyethylene glycol dialkyl ethers and some sulphur analogues measured by gas chromatography

Abstract Gas—liquid chromatography was used to determine the polarity of pure model polyoxyethylene glycol dialkyl ethers and their sulphur analogues. Relationships between the polarity parameters are discussed. The polarity parameters were correlated with surfactant structure and increments for characteristic groups were determined.

Influence of prediction method of the second virial coefficient on inverse gas chromatographic parameters

Abstract Methods of prediction of the second virial coefficient which may be used in calculation of inverse gas chromatographic parameters are presented. It is shown that these predictions led to various B11-values. Moreover, the final result, i.e. Flory-Huggins interaction parameter κ1,2∞ and/or mass activity coefficient Ω 1 ∞ is also different. However, the relative differences between inverse gas chromatographic parameter are one order of magnitude lower than those of the second virial coefficient. Variations in inverse gas chromatographic parameters depend also on the stationary phase used.

Inverse gas chromatography. Relationship between mass activity coefficient and flory-huggins interaction parameter in the examination of petroleum pitches

SummaryThe use of the basic relations for the calculation of the weight fraction activity coefficient Ω1∞ and the Flory-Huggins interaction parameter ϰ12∞ requires the knowledge of the density and the molecular mass of the stationary phase. As these data are often inaccessible the use of a simplified equation is examined. The errors generated during the calculation of ϰ12∞ and solubility parameter δ2 are presented and discussed. All experimental data were collected for the series of fractions separated from high-boiling vacuum distillation residues of petroleum.

Acid-based properties of silicas modified by organic compounds as determined by inverse gas chromatography

Abstract The results of silica surface modification by selected modifiers were examined by inverse gas chromatography (IGC). Experiments were carried out at infinite dilution and Gibbs free energies and enthalpies of specific interactions were determined according to Papirers and Dong-Donnets approaches, KA and KD values, calculated from enthalpies of specific interactions, as well as their ratio Sc = KD/KA, were used for characterization of the examined surfaces. The influence of the modifier type and its amount upon the physicochemical parameters investigated is presented and discussed.