Inverse Gas Chromatography Experiments Research Articles

Investigation of Physicochemical Characteristics of Aspergillus niger Biomass and Examination of Its Ability to Separate Butyl Acetate Isomers.

Aspergillus niger is a species of fungus that is widely found in natural ecosystems and has an important role in various industrial fields and is readily available. To study the adhesion of microbial cells to solid substrates and to improve their properties, physicochemical characterization of microorganisms is extremely important. For this purpose, in this study, the surface properties of A. niger biomass were determined at low cost and with high accuracy by inverse gas chromatography (IGC), a physicochemical characterization technique. IGC experiments were conducted between 303.2 and 328.2K at infinite dilution. Among these temperatures, various organic solvent vapors were passed over the A. niger biomass considered as stationary phase and their retention behavior was studied. Using the raw data, net retention volumes were calculated and retention diagrams were drawn. From the linear retention diagrams, the dispersive surface energy was calculated according to Dorris-Gray (48.73-46.09 mJ/m2), Donnet-Park (47.12-44.50 mJ/m2), Schultz (46.88-42.45 mJ/m2), and Hamieh (76.42-64.06 mJ/m2) methods. With the IGC method, the acidity-basicity parameters of A. niger biomass were determined and it was found that the surface was basic ( ). In the second part of this study, the butyl acetate isomer series, which are difficult to be separated by conventional methods, were effectively separated by the IGC method using A. niger stationary phase.

Characterization of polar surface groups on siliceous materials by inverse gas chromatography and the enthalpy-entropy compensation effect.

Surface-modified porous silica is a well-established composite material. To improve its embedding and application behavior, adsorption studies of various probe molecules have been performed using the technique of inverse gas chromatography (IGC). For this purpose, IGC experiments were carried out in the infinite dilution mode on macro-porous micro glass spheres before and after surface modification with (3-mercaptopropyl)trimethoxysilane. To provide information about the polar interactions between probe molecules and the silica surface, in particular, eleven polar molecules have been injected. In summary, the free surface energy for pristine silica ( = 229mJ/m2) and for (3-mercaptopropyl)trimethoxysilane-modified silica ( = 135mJ/m2) indicates a reduced wettability after surface modification. This is due to the reduction of the polar component of the free surface energy ( ) from 191mJ/m2 to 105mJ/m2. Simultaneously, with the reduction of surface silanol groups caused by surface modification of silica and, therefore, the decrease in polar interactions, a substantial loss of Lewis acidity was observed by various IGC approaches. Experiments with all silica materials have been conducted at temperatures in the range from 90°C to 120°C to determine the thermodynamic parameters, such as adsorption enthalpy ( ) and adsorption entropy ( ), using the Arrhenius regression procedure evaluating the IGC data. With the help of the enthalpy-entropy compensation, two types of adsorption complexes are assumed between polar probe molecules and the silica surface because of different isokinetic temperatures. Identical adsorption complexes with an isokinetic temperature of 370°C have been assigned to alkanes and weakly interacting polar probes such as benzene, toluene, dichloromethane, and chloroform. Polar probe molecules with typical functional groups such as OH, CO, and CN, having the ability to form hydrogen bonds to the silica surface, exhibit a lower isokinetic temperature of 60°C. Quantum chemical calculations of the probe molecules on a non-hydroxylated and hydroxylated silica cluster supported the formation of hydrogen bonds in the case of a strong polar adsorption complex with a bonding distance of 1.7nm-1.9nm to the silica surface.

The ideal treatment for heart failer

The acid-base characteristics of the catalyst material are frequently linked to catalytic activity. Metal-organic frameworks (MOFs) have been tested as catalysts for a variety of processes. Based on the observed performance in diverse catalytic processes, Cu-BTC (with a well-defined crystalline structure) and Fe-BTC (with a gel-like porous structure) have both shown the presence of Lewis surface acid sites. In this study, researchers used Inverse Gas Chromatography (IGC) and n-butylamine thermal desorption analysis to assess the acid-base characteristics of both materials. Using acidic, basic, and amphoteric molecules, IGC experiments can access the acid-base characteristics of the material surface. The n-butylamine thermal desorption measurements, on the other hand, allow quantification of those acid and basic sites from the n-butylamine desorption curves of a sample previously saturated with that probe molecule. The Lewis acid properties obtained by both methodologies showed to be more pronounced for the Fe-BTC MOF sample. The IGC measurements exhibited values of acidity constants (KA) of 0.81 and 0.60 for Fe-BTC and Cu-BTC, respectively. Furthermore the n-butylamine thermo desorption experiments indicate total acidities of 2.06 and 0.49 mmol g−1 for Fe-BTC and Cu-BTC, respectively.

A detailed surface characterization study of SBA-15 and B-SBA-15-x mesoporous materials using the IGC technique

Pure and boron-containing B-SBA-15-x (molar ratio, Si/B = 50, 30, 10) mesoporous materials were synthesized by a direct hydrothermal procedure. Samples were characterized by XRD, ICP-OES, FT-IR, BET and SEM. Inverse gas chromatography (IGC) technique was used to determine the dispersive surface energies (γSd), adsorption thermodynamic parameters (ΔH, ΔG, ΔS) and the acid-base constants (KA and KD) of the samples. IGC experiments were performed at infinite dilution region at 200, 210, 220 and 230 °C. The surface characterization results confirmed that the SBA-15 structure was formed, boron was added to the structure and all samples have meso pores. The surface area of the pure SBA-15 was determined as 745.288 m2/g and it was found that the surface area decreases with increasing boron content. Physical adsorption occurred between the IGC probe molecules and all SBA-15 materials according to the adsorption thermodynamic parameters. (γSd) values of pure SBA-15, B-SBA-15-50, B-SBA-15-30 and B-SBA-15-10 were found at 40.873, 37.039, 36.636 and 37.444 mJ/m2 at 200 °C, respectively. It has been observed that the dispersive surface energy of all samples decreases with increasing temperature. According to the SC value calculated from the KA and KD parameters, the surface of B-SBA-15-10 with the highest boron content was found to be acidic. On the other hand the surfaces of all other samples were determined as basic.

Quantitative Study on Solubility Parameters and Related Thermodynamic Parameters of PVA with Different Alcoholysis Degrees.

In recent years, inverse gas chromatography (IGC) and molecular dynamics simulation methods have been used to characterize the solubility parameters and surface parameters of polymers, which can provide quantitative reference for the further study of the surface and interface compatibility of polymer components in the future. In this paper, the solubility parameters and surface parameters of two kinds of common alcoholysis, PVA88 and PVA99, are studied by using the IGC method. The accuracy of the solubility parameters obtained by the IGC experiment is verified by molecular dynamics simulation. On the basis of this, the influence of repeated units of polyvinyl alcohol (PVA) on solubility parameters is studied, so as to determine the appropriate chain length of the PVA for simulation verification calculation. The results show that the solubility parameters are not much different when the PVA chain length is 30 and above; the numerical trends of the solubility parameters of PVA88 and PVA99 at room temperature are the same as the results of molecular dynamics simulation; the dispersive surface energy and the specific surface energy are scattered with the temperature distribution and have a small dependence on temperature. On the whole, the surface energy of PVA99 with a higher alcoholysis degree is higher than that of PVA88 with a lower alcoholysis degree. The surface specific adsorption free energy () indicates that both PVA88 and PVA99 are amphoteric meta-acid materials, and the acidity of PVA99 is stronger.

Inverse gas chromatography in the examination of surface properties of experimental dental composites

Properties of the surface layer of materials determine their suitability for some special applications, affecting the value of adhesion between bonding materials. In the case of dental fillings, the high value of adhesion to tooth tissue is important and determines their durability and tightness. The surface properties of dental methacrylic resin with the addition of various zeolite fillers were examined using inverse gas chromatography (IGC). The dispersive and specific component of the surface energy, acceptor – donor properties were determined from IGC experiments. The effect of the addition of zeolite filler on the surface energy values of the examined dental composites was investigated. It has been shown that using IGC it is possible to determine parameters describing the adhesion between materials, expressed by the value of the work of adhesion. Different values of the work of adhesion were observed according to the type of tooth tissue (dentin or enamel).

Morphological and Physicochemical Evaluation of Two Distinct Glibenclamide/Hypromellose Amorphous Nanoparticles Prepared by the Antisolvent Method.

The morphology and stability of amorphous nanoparticles of glibenclamide (GLB) prepared by the antisolvent method using different methods of adding hypromellose (HPMC) were evaluated. Nano-A was prepared by the injection of a dimethyl sulfoxide (DMSO) solution of GLB into the HPMC solution, whereas nano-B was obtained by the injection of a DMSO solution of GLB and HPMC into water. Cryogenic transmission electron microscopy, field-emission scanning electron microscopy, and field-emission transmission electron microscopy, including energy dispersive X-ray spectrometry, revealed that the particles of the nano-A and nano-B samples are hollow spheres and nonspherical nanoparticles, respectively. Powder X-ray diffraction and solid-state NMR measurements showed that GLB is present in an amorphous state in both nano-A and nano-B. The weight ratios of HPMC in the GLB/HPMC nanoparticles were 11 and 16% for nano-A and nano-B, respectively, as determined by solution-state NMR. The glass transition temperatures ( Tg) of nano-A and nano-B evaluated using differential scanning calorimetry were lower by about 10 °C compared to that of amorphous GLB, presumably because of a Tg confinement effect and the surface coverage and mixing of HPMC, as suggested by the inverse gas chromatography experiment. GLB crystallization during storage was suppressed more strongly in nano-B than nano-A, owing to the higher amount of HPMC and the higher miscibility between GLB and HPMC. It is suggested that the diffusion rate of the solvent during nanoprecipitation determined the nanoparticle properties. In nano-A, the precipitation of GLB first occurred at the outer interface because of the rapid diffusion of the solvent. Thus, hollow spherical particles with HPMC preferentially located near the surface were formed. On the other hand, the diffusion of the solvent in nano-B was suppressed because of the presence of HPMC, yielding small nonspherical nanoparticles with a high miscibility of GLB and HPMC.

Inverse gas chromatography (IGC) as a tool for an energetic characterisation of porous materials

The surface properties of controlled pore glass, silica gel and ordered mesoporous silica SBA-15 having different functional groups (hydroxyl, trimethylsilyl and aminopropyl) were investigated by inverse gas chromatography. The porous silicates were used as model system to study correlations between surface chemistry and surface energy by means of the IGC technique. The van Deemter equation was used for the determination of optimum carrier gas flow rate. The dispersive part of surface energy, the specific free energy of adsorption, acceptor–donor properties and heat of adsorption were determined from IGC experiments for an energetic characterisation of the porous materials. It is shown that different surface functional groups have an influence onto dispersive interactions with n-alkanes as well as onto the specific interactions with polar molecules.

Surface energy of minerals – Applications to flotation

Inverse gas chromatography (IGC) is a versatile and powerful technique for characterizing physicochemical properties of materials. One such property, the surface energy, plays an important role in the adhesiveness, wettability, and consequently flotation of minerals. In this work, quartz was chosen as a naturally hydrophilic mineral, and dodecylamine was used to hydrophobise the surface. To study the correlation between the surface properties as measured from IGC experiments and flotation, microflotation experiments were also conducted. It was shown that with treatment by dodecylamine, the surface energy decreased, as did the work of adhesion to water. The recovery of quartz increased after the treatment, indicating a correlation between surface energy and flotation response.The results indicate that IGC has the capability to determine the thermodynamic properties of quartz, pre- and post-conditioning. Relating the hydrophobicity and flotation of minerals to the surface energy can be observed from combining the results of IGC and microflotation experiments.

Characterization of a Compound Starch-Based Adsorbent for Alcohol—Water Azeotrope Dehydration

Biosorptive dehydration processes of ethanol, isopropanol and t-butyl alcohol (TBA) using a specially formulated compound starch-based adsorbent (CSA) were investigated and analyzed. The inverse gas chromatography (IGC) experimental results indicated that the CSA was effective for the selective separations at the alcohol and water azeotropes. Using batch adsorption and regeneration experiments, the optimal adsorption and regeneration conditions were determined by single-factor and orthogonal design methods. A comparison of the results from the IGC and batch adsorption experiments of the three azeotrope systems suggested that the separation factors increased with decreasing alcohol polarities and increasing numbers of alcohol carbon atoms, which may be related to the transport properties and strength of the interactions between the alcohol and free OH groups on the glucose units in the CSA. The field emission scanning electron microscopic images and pore-size distributions indicated that the main component...

Characterization of the Solvent Properties of Glycerol Using Inverse Gas Chromatography and Solubility Parameters

AbstractThe production of glycerol from the synthesis of biodiesel has led to a market surplus of this polyhydric alcohol and additional research to find new applications for this versatile chemical. This study involves the use of inverse gas chromatography (IGC) to characterize the solute–solvent interactions between glycerol and a homologous series of aliphatic alcohols, in which the latter components are at infinite dilution in the glycerol, which is the stationary phase contained in a packed GC column. The IGC experiments were conducted between 51.5 and 111 °C for the n‐alcohols ranging from methanol to n‐butanol. All of the n‐alcohol homologs exhibited positive deviations from Raoult's law as based on mole fraction activity coefficients values ranging from 1.86 to 14.4. The measured mole fraction activity coefficients of the alcoholic solutes in glycerol showed good agreement with literature values, and in some cases with those predicted using existing theoretical models. The mole fraction activity coefficients increased going from methanol to n‐butanol, reflecting the change in the alcohol's cohesive energy densities relative to that for glycerol. The total solubility parameter of glycerol calculated from IGC data was found to be 34.8 MPa1/2 which is in good agreement with that obtained using Hansen solubility parameter approach (31.6 MPa1/2). This data can be used to characterize the solvent properties of glycerol as well as to provide thermodynamic data for the removal of the alcoholic solutes from glycerol.

Monitoring surface properties evolution of thermochemically modified cellulose nanofibres from banana pseudo-stem

Abstract The effect of steam explosion coupled with chemical treatment, on the surface properties of banana fibres obtained from the pseudo-stem of banana plant Musa sapientum was studied in detail by inverse gas chromatography (IGC). IGC experiments were performed in banana fibres from macro to nano stages at 293, 298 and 303 K. The analyzed fibres showed dispersive component of the surface energy between 39.59 and 48.03 mJ/m2, at 298 K. The interaction between the fibres and the high and low DN/AN* probes indicate the presence of both acidic and basic active sites on the fibres surface. The values of Ka and Kb suggest that predominantly basic active sites are involved in the specific adsorption process in the nanofibres. During the thermochemical treatment, changes occur in the arrangement of macromolecular chains with the reduction of dispersive groups and the increase in some polar groups. This susceptibility of the surface to change its acid–base characteristics combined with a change in dispersive properties enhance the possibility of specific intermolecular interactions with different solvents, plasticizers, polymers or fillers, which is important to the practical applications of the nanofibres.

Surface energetics of bone mineral and synthetic hydroxyapatite using inverse gas chromatography

Surface energy is one of the important factors that govern protein adhesion and cell attachment on biomaterial surfaces. Inverse gas chromatography (IGC) provides an excellent method to measure the surface energetics of rough and porous biosurfaces. In this study IGC was used to characterize and compare the surface energetics of synthetic and biological hydroxyapatites (natural bone mineral). IGC experiments were performed on three samples: synthetic hydroxyapatites with two levels of purity (99% and 90%) and natural biological hydroxyapatite obtained from bovine trabecular bone. The Lifshitz–Van der Waals component of the surface free energy ( γ S L W ) and specific interaction parameter ( ɛ π) were determined by using homologous series of n-alkanes and alkenes as IGC probe molecules, respectively. The synthetic hydroxyapatite had values of γ S L W of 33.4 mJ m −2 at 99% purity and 53.3 mJ m −2 at 90% purity. Biological hydroxyapatite had a value of γ S L W of 45.7 mJ m −2. For the synthetic hydroxyapatite, the values of π-bond specific interaction parameters, ɛ π, were 0.95 mJ (99%) and 3.01 mJ (90%). The biological hydroxyapatite sample had a value of 2.44 mJ for ɛ π. The results suggest that, as compared to the synthetic compounds, the biological apatite has considerable surface heterogeneity, either chemical (impurities) or structural suggesting a scaffold surface that is more conducive of protein adhesion and cell attachment.

On the effect of a non-ionic surfactant on the surface of sucrose crystals and on the crystal growth process by inverse gas chromatography

The effect of Hodag CB6, a widely used non-ionic surfactant in sugar crystallization process, on the surface properties of sucrose was studied in detail by inverse gas chromatography (IGC) experiments. IGC experiments were performed with pure sucrose crystals, surfactant coated sucrose crystals, and crystals grown in the presence of surfactant at 313.05 and 323.05 K. The surfactant promotes the specific interactions with the polar probes. The sorption of basic, acidic and amphoteric probes onto pure and surfactant coated sucrose was found to be endothermic and in the case of neutral probes was found to be exothermic. The surfactant increases both the acidity and basicity of the sucrose surface with the latter effect being significant. The role of interfacial tension on the growth kinetics of sucrose crystals was studied using IGC for different surfactant concentrations. IGC results with the surfactant coated sucrose were used to interpret the thermodynamic effect of surfactants during the crystal growth process. The dispersive component of the surface energy, γ s D , of surfactant coated sucrose crystals was found to be lower than that of pure sucrose crystals and was found to be in the range of 33.49–35.27 mJ/m 2.

Determination of Flory interaction parameters between polyimide and organic solvents by HSP theory and IGC

Flory-Huggins interaction parameter χ12 is an important parameter used for characterizing the interaction intensity between polymer and solvent. In this work, two methods were used to calculate the χ12 values of a polyimide (HQDPA-DMMDA) and twelve organic solvents. One method was inverse gas chromatography (IGC) technique, another was Hansen Solubility Parameters (HSP) theory. For the IGC experiment, χ12 was measured with an extrapolation method for the carrier gas when the temperature was changed from 50circC to 80°C. For the HSP approach, the Beerbower group contribution method was used to calculate the HSP values of the polyimide. It was found that the χ12 values of the polyimide and the organic solvents calculated from the two methods were similar. Consequently, the Beerbower group contribution method can be used to calculate HSP, and the HSP can be used to rapidly estimate the Flory–Huggins interaction parameter χ12.

Use of Flory–Huggins parameters in the characterization of polymer–filler compositions

AbstractAny quantitative information on the strength of interactions between an inorganic filler and polymer is substantial for the future application of the composite. The magnitude of adhesion of two phases may be deduced from results collected by various experimental techniques. A Flory–Huggins interaction parameter (χ23′) was earlier successfully used in the characterization of polymer blends. We propose to express the magnitude of modified filler/polymer interactions by using χ23′. It was calculated from retention data of test solutes during an inverse gas chromatography (IGC) experiment. IGC is an extension of conventional gas chromatography in which a nonvolatile material to be investigated is immobilized on a column. Parameters determined during IGC experiments may be successfully used in the characterization of polymers and their blends, composites, fillers, and other materials and the quantification of the interactions between the components of polymer mixtures, including the interactions between polymeric components and filler surfaces. Here this method is applied to the characterization of a series of poly(ether urethane)/modified carbonate–silicate filler systems containing different amounts of a filler (5, 10, and 20 wt %). The possibilities and limitations of the IGC method are shown. The usefulness of some methods for minimizing the Δχ effect (the dependence of χ23′ on the type of test solute) is examined and discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Elastic effects on solubility in semicrystalline polymers

AbstractCapillary column inverse gas chromatography experiments at infinite solvent dilution were conducted for 15 polyethylene/solvent systems. Thermodynamic data were collected for various types of penetrant molecules (normal alkanes, 1‐alkenes, isomers of hexane, and ring compounds). Theoretical predictions of the solubility data were made with an activity coefficient model (Universal Functional Group Activity‐van der Waals‐Free‐Volume) (UNIFAC‐vdw‐FV) and an equation‐of‐state model (Group‐Contribution, Lattice‐Fluid, Equation of State) (GCLF‐EoS). Although good agreement between the experimental data and theoretical predictions was obtained above the melting point of the polymer, at temperatures below the melting point, significant differences were found. This occurred because at those temperatures, the polymer had a semicrystalline structure and the solubility of the solvent was reduced on account of the constraints on some of the chains in the amorphous phase by the polymer crystallites. The theory developed by Michaels and Hausslein to account for such elastic effects on solubility was incorporated into the two predictive models. After these modifications, the new estimations of the solubility showed significantly improved agreement with the experimental results. Moreover, the elasticity effect resulted in elevated estimates of the crystallinity when inverse gas chromatography retention volumes were used. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Application of inverse gas chromatography for polymer characterization

The possibility of polymer characterization by inverse gas chromatography (IGC) was illustrated with the study of sorption properties of macroporous crosslinked poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate), PGME, synthesized by suspension copolymerization, and copolymer modified with ethylene diamine, PGME-en. The data collected from IGC experiments at infinite dilution are used for the calculation of the thermodynamic parameters of adsorption, dispersive components of the surface free energies, and the acid/base constants. .

Anisotropic surface chemistry of crystalline pharmaceutical solids

The purpose of this study was to establish the link between the wetting behavior of crystalline pharmaceutical solids and the localized surface chemistry. A range of conventional wetting techniques were evaluated and compared with a novel experimental approach: sessile drop contact angle measurements on the individual facets of macroscopic (>1 cm) single crystals. Conventional measurement techniques for determining surface energetics such as capillary rise and sessile drops on powder compacts were found not to provide reliable results. When the macroscopic crystal approach was used, major differences for advancing contact angles, theta(a), of water were observed-as low as 16 degrees on facet (001) and as high as 68 degrees on facet (010) of form I paracetamol. theta(a) trends were in excellent agreement with X-ray photoelectron spectroscopy surface composition and known crystallographic structures, suggesting a direct relationship to the local surface chemistry. Inverse gas chromatography (IGC) was further used to probe the surface properties of milled and unmilled samples, as a function of particle size. IGC experiments confirmed that milling exposes the weakest attachment energy facet, with increasing dominance as particle size is reduced. The weakest attachment energy facet was also found to exhibit the highest theta(a) for water and to be the most hydrophobic facet. This anisotropic wetting behavior was established for a range of crystalline systems: paracetamol polymorphs, aspirin, and ibuprofen racemates. theta(a) was found to be very sensitive to the local surface chemistry. It is proposed that the hydrophilicity/hydrophobicity of facets reflects the presence of functional groups at surfaces to form hydrogen bonds with external molecules.

Surface energetics of cementitious materials and their wettability by an epoxy adhesive

The surface thermodynamic properties of cementitious materials and the wettability of these substrates by an epoxy adhesive were investigated using various surface analysis techniques. In a first step, surface energies of hardened cement pastes were assessed either by contact angle measurements using the Owens and Wendt approach, or by inverse gas chromatography (IGC). A good correspondence was found between the two techniques for the dispersion contribution γ s d , and a strong amphoteric behavior of these materials was also demonstrated. Additionally, a surface carbonaceous contamination detected by X-ray photoelectron spectroscopy (XPS) was found to lower the surface energy of as-received samples, whereas an acetone cleaning treatment resulted in increased γ s d values. In a second part, surface characterizations were performed on three synthetic compounds, representative of the main hydration products of hardened cement pastes, i.e. calcium hydroxide, ettringite and calcium silicate hydrate (C -S -H). IGC experiments provided γ s d values ranging from 45.6 up to 96.3 mJ m −2 at 35 °C, and the acid–base behavior was correlated to the water content. Last, XPS and IGC analyses were performed on cement paste powders coated either with an epoxy resin (R) or with an amine hardener (H), separately, at mass loadings up to 10 wt.%. Changes in the dispersion contribution to the surface energy ( γ s d ) and Lewis acid–base interaction energy were found to be significantly dependent on the adsorption of both H and R, showing a substantial wetting of the mineral substrate by the adhesive components. In addition, XPS evidenced interfacial hydrogen bonding between the hardener and the cementitious substrates.