Use Of Inverse Gas Chromatography Research Articles

Exploring affinity between organic probes and Prussian Blue Analogues via inverse gas chromatography

Prussian Blue Analogues (PBAs), which are characterized by their open structure, high stability, and non-toxic properties, have recently been the subject of research for various applications, including their use as electrode precursors for capacitive deionization, gas storage, and environmental purification. These materials can be readily tailored to enhance their affinity towards gases for integration with sensing devices. An improved understanding of PBA-gas interactions is expected to enhance material development and existing sensor deposition schemes greatly. The use of inverse gas chromatography (IGC) is a robust approach for examining the relationship between porous materials and gases. In this study, the adsorption properties of (functionalized) hydrocarbons, i.e., probe molecules, on the copper hexacyanoferrate (CuHCF) lattice were studied via IGC, demonstrating that alkylbenzenes have a higher affinity for this material than n-alkanes. This difference was rationalized by steric hindrance, π–π interactions, and vapour pressure effects. Along the same line, the five isomers of hexane showed decreasing selectivity upon increased steric hindrance. Enthalpy values for n-pentane, n-hexane and n-heptane were lower than that of toluene. The introduction of increased probe masses resulted in a surface coverage of 46% for toluene. For all n-alkane probe molecules this percentage was lower. However, the isotherms of these probes did not show saturation points and the observed linear regime proves beneficial for gas sensing. Our work demonstrates the versatility of CuHCF for gas sensing purposes and the potential of IGC to characterize the adsorption characteristics of such a porous nanomaterial.

Influence of the matrix and polymerization methods on the synthesis of BC/PANi nanocomposites: an IGC study

Inverse gas chromatography (IGC) is a technique for evaluating surface properties. The current work emphasizes the use of IGC to evaluate the surface physicochemical changes during different bacterial cellulose (BC) processing methods as well as upon polyaniline (PANi) incorporation. The processing methods (oven-drying, freeze-drying, and regeneration) caused changes in the BC surface group distribution, where upon freeze-drying and regeneration, a more acidic behavior is obtained, compared to oven-drying (Kb/Ka decreased up to 24%). Through freeze-drying, the structural pore preservation increases (54%) the BC porosity, whereas through regeneration, the porosity decreases (23%), compared to BC oven-drying. Regarding the nanocomposites, with PANi incorporation, the overall properties evaluated by IGC were significantly changed. The $$\gamma_{\text{s}}^{\text{total}}$$ increases up to 150%, indicating a more reactive surface in the nanocomposites. Also, is observed a sevenfold increase in the Kb/Ka and a less porous surface (up to 85%). Hence, the current work highlights the use of IGC as a viable technique to evaluate the physicochemical changes upon different BC modifications.

The effect of bonding system application on surface characteristics of bovine dentin and enamel

The main objective of this study was to examine the surface changes of bovine teeth hard tissues (dentin and enamel) after surface preparation with the use of commercial 3-component etch-and-rinse bonding system. Surface composition changes, morphology, BET specific surface area and surface energy parameters were examined after etching, application of primer and adhesive. Characteristic of tissues composition was carried out with the use of Raman spectroscopy. Morphological changes were followed by scanning electron microscopy, while specific surface area values were measured by the means of gas porosimetry. For the first time surface energy of prepared teeth hard tissues was studied with the use of inverse gas chromatography. A detailed characteristic of surface parameters of bovine teeth hard tissues was made. Obtained results show that each step of dentin and enamel preparation is reflected in all studied parameters. Application of etchant, primer and adhesive causes an increase of surface activity of all examined tissues, measured as surface energy parameters. Surface parameters changes caused by the application of bonding system are crucial from dentin/enamel – restorative material adhesion point of view.

Preparation of hybrid materials for controlled drug release

Authors obtained hybrid organic–inorganic materials applied in sustained drug delivery. The materials are ibuprofen as a model drug, hydroxyapatite and three different polymers as supports. Influence of the type of employed polymer, an inorganic carrier, on the properties and drug release profiles was estimated. Flory–Huggins interaction parameters, the dispersive component of surface free energy and acid-base characteristic of the surface were used to assess the behavior of the composites in terms of drug release. The experiments were carried out with the use of inverse gas chromatography (IGC), Fourier transform infrared (FTIR) and ultraviolet (UV) techniques. FTIR and ATR-FTIR spectra were collected. The values of parameter obtained for all investigated materials (excluding poly(L-lactide) (PLA2)) indicate low or medium activity. The strongest interactions (the lowest values of the Flory–Huggins parameter) are observed for PLA2 composition, while the weakest interactions for systems with polyethylene glycol (PEG). Finally, drug release profiles are shown. For materials prepared with Eudragit® (EUD) and PLA, the release of drug was much smaller, which corresponds to lower values of Flory–Huggins parameter. The executed experiments allowed the estimation of the properties of prepared composites. Prepared materials present properties required in sustained drug release and may be successfully applied as drug delivery systems.

Surface energy of bovine dentin and enamel by means of inverse gas chromatography.

Adhesion between tooth tissues and dental fillings depends on the surface energy of both connected materials. Bond strength can be determined directly or indirectly as a work of adhesion on the basis of values of surface energy of these materials. Inverse gas chromatography (IGC) is one of the methods of surface energy examination. In this study the values of total surface energy components of wet and dry teeth fragments (enamel, crown dentin and root dentin) were determined with the use of inverse gas chromatography. Inverse gas chromatography has never been used for investigation of surface energy of natural tooth tissues. Different storage conditions were examined - wet and dry. Different values of surface energy are observed according to the type of tooth tissue (dentin or enamel), occurring place (crown or root) and storage conditions (dry or wet). The effect of tissue type and occurring place was the greatest, while storage conditions were of secondary importance. Surface energy depends on composition of tissue, its surface area and the presence of pores.

Application of inverse gas chromatography in physicochemical characterization of phenolic resin adhesives

One of the most important stages during production of abrasive tools is their hardening. The degree of hardening is very important and influence toughness of the final product. During hardening process the cross-linking of the phenolic resins, used as a binder, occurs. Nowadays, there is no standard, accurate and simple method for the estimation of the hardening degree of abrasive tools. The procedure of the determination of hardening degree of the binder (phenolic resins) by means of inverse gas chromatography (IGC) was presented in this paper. Results obtained by use of IGC derived method was verified by Soxhlet extraction and by FTIR method. Good agreement was found for results from IGC and Soxhlet extraction whereas those from FTIR were much lower. FTIR method supplies data concerning bulk properties not the surface as in case of IGC and Soxhlet methods. These results indicate that resins are more cross-linked on the surface than inside the material.

Surface properties of solid materials measured by modified inverse gas chromatography

A novel modified inverse gas chromatography (IGC) method has been developed to investigate the surface properties of solid materials. On the modified IGC system, the every adjusted retention time of miscellaneous probe molecules can be rapidly calculated within only one sample injection through wisely induction a capillary column and two detectors, i.e., flame ionization detector (FID) and thermal conductivity detector (TCD). In the system, the relative dead time can be acquired from FID detector while the retention time can be obtained from TCD detector simultaneously. The significant advantage of our design is that, experimental time is greatly saved compared to the traditional IGC. In addition, the new system is capable of distinguishing variety surface properties of porous materials. Two types of active carbon samples were tested, and the results showed that their thermodynamic parameters were quite different, indicating that the samples have opposite acidic/basic properties. The use of IGC would be an effective tool to evaluate the physiochemical data of solid materials.

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.

Badanie metoda inwersyjnej chromatografii gazowej wplywu wielkosci podstawnika na wlasciwosci inkluzyjne kaliksarenow

The effect of the size of aliphatic substituent on the inclusion properties of calixarenes {calix[4]arene, p-isopropyl calix[4]arene (IPK4) and p-tert-butyl calix[4]arene (TBK4)} was investigated. QSRR method with use of inverse gas chromatography were applied for the assessment of this effect. Aliphatic alcohols, benzene homologues and homologues of pyridine were used as solutes. It has been found, on the basis of Kováts's retention indices and the diagrams of dependence of specific retention volume on boiling point [Vg=f(Tw)] that only substituted calixarenes showed inclusion properties towards lower alcohols and pyridine (Fig. 1-3, Table 1).

Use of inverse gas chromatography for the physicochemical characterisation of a new synthesised liquid crystal: (S)‐5‐(2‐methylbutoxy)‐2‐{[(4‐dodecyloxyphenyl)imino]methyl}phenol

A new liquid crystalline compound, i.e. (S)‐5‐(2‐methylbutoxy)‐2‐{[(4‐dodecyloxyphenyl)imino]methyl}phenol (MBDOPIMP), was prepared and characterised. Phase transition temperatures of MBDOPIMP were determined by polarising optical microscopy and differential scanning calorimetry. Trace amounts of ethyl acetate, butyl acetate, isobutyl acetate, hexane, heptane, octane, nonane and decane were passed through a chromatographic column loaded with MBDOPIMP coated on Chromosorb W. The retention diagrams of the solvents on MBDOPIMP were plotted using specific retention volumes at temperatures between 105 and 125°C. Thermodynamic parameters, such as Flory–Huggins liquid–solvent interaction, , equation‐of‐state liquid–solvent interaction, , effective exchange energy, X eff, the exchange enthalpy, X 12 and exchange entropy, Q 12, were determined for the liquid crystal–solvent systems. Subsequently, the partial molar heats of sorption, ΔH¯1,sorp and mixing, , were determined from the slopes of the plots of the logarithm of the specific retention volume, ln , versus 1/T and logarithm of the weight fraction activity coefficients, ln , versus 1/T, respectively.

The Use of Inverse Gas Chromatography (IGC) to Determine the Surface Energy of RDX

AbstractThe surface properties of RDX play an important role in enhancing mechanics performances of the propellants and explosives. In this work, thereby, inverse gas chromatography (IGC) using various probe liquids as the medium was used to determine the surface energy components of RDX containing both dispersive and polar components, which were acquired respectively from neutral probe liquids (such as n‐hexane, n‐heptane, n‐octane) and polar probe liquids (such as chloroform, benzene, methanol). The results show that RDX located in different column temperatures has difference in the surface energy and possesses more surface energy when there is high temperature. The calculated formula of the total surface energy with temperature is: $\rm{ {\rm{\gamma }}_{\rm{s}}^{\rm{T}} {\rm{ = }} - {\rm{82}}{\rm{.16}} + }$ $\rm{{\rm{0}}{\rm{.3557}}T}$, and it is also found that dispersive, polar, electron acceptor, and electron donor components of RDX are $\rm{{\rm{\gamma }}_{\rm{s}}^{{\rm{LW}}} {\rm{ = }} - {\rm{53}}{\rm{.29}} + {\rm{0}}{\rm{.2560}}T}$, $\rm{ {\rm{\gamma }}_{\rm{s}}^{{\rm{AB}}} {\rm{ = }} - {\rm{28}}{\rm{.57}} + {\rm{0}}{\rm{.09889}}T}$, $\rm{ {\rm{\gamma }}_{\rm{s}}^{\rm{ + }} {\rm{ = }} - {\rm{25}}{\rm{.82}} }$ $\rm{+ {\rm{0}}{\rm{.08943}}T}$, and $\rm{ {\rm{\gamma }}_{\rm{s}}^ - {\rm{ = }} }$ $\rm{- {\rm{7}}{\rm{.932}} + {\rm{0}}{\rm{.02743}}T}$, respectively. These results demonstrate that the dispersive component is the primary part of the total surface energy, and RDX has an acid performance.

Infinite dilution diffusion coefficients of organic solvents in nascent polyethylene particles by inverse gas chromatography measurements

AbstractDiffusion coefficients of four organic solvents: dichloromethane, trichloromethane, tetrachloromethane and n-hexane in polyethylene particles at infinite dilution were determined by use of inverse gas chromatography (IGC). The polymer particles were used as supplied by the producer to pack the chromatographic columns. This allowed a direct measurement of the interested properties in a particle with the same morphology obtained at the reactor outlet. The particle morphology was investigated and classical mathematical model for chromatographic process was adopted based upon the analysis of particle microstructure. It was found that the limitation step for mass transfer was in the polymer matrix rather than in macropores, and when interpreted in terms of diffusion coefficients for spherical particles, the measured diffusion coefficients compared favourably with predicted values from literature relationships and free volume theory.

Shear strength at Sisal fibre–polyester resin interfaces: use of inverse gas chromatography to study pretreatment effects

Inverse gas chromatography, IGC, has been used to investigate changes to the surface of Sisal fibres on treatment with sodium hydroxide. By determining the retention of a series of alkane probes and of probes with acidic or basic character, it was shown that little change to the chemical nature of the surface occurs as measured by the enthalpy of adsorption of alkane probes or the dispersion component of the surface free energy. This IGC study supports the conclusion of previous work involving S.E.M. which suggested that the major effect of the treatment was the removal of weak or adventitious layers from the substrate surface, thus increasing the interfacial shear strength when incorporated into polyester resin.

Use of inverse gas chromatography to account for the pervaporation performance in monitoring the oxidation of primary alcohols

The oxidation of n-propanol and n-butanol to their corresponding aldehydes was monitored by the pervaporation technique. Mass transfer phenomenon that occurs in the pervaporation process was confirmed by the results of inverse gas chromatography. Polydimethylsiloxane (PDMS), a hydrophobic polymer widely employed as a membrane in pervaporation technique, was evaluated as a stationary phase in this study. The retention times of the different molecules probes ( n-propanol, n-butanol, propionaldehyde, and butyraldehyde), molecules involved as reactants and products in the oxidation reaction, gave an insight into the extent of the interactions between each of these molecules and the stationary phase. The infinite dilution conditions allowed to measure the infinite dilution activity coefficient, γ ∞, and the specific retention volume, V g 0 , and to estimate the Flory-Huggins parameter interactions, χ 12 ∞ . The magnitudes of these parameters threw some light on the permselectivity of the membranes in the pervaporation operation.

The use of inverse gas chromatography to study surface thermal oxidation of polypropylene

Thermo-oxidative effects on the surface energy of polypropylene were measured by inverse gas chromatography as a function of exposure time and temperature. Unaltered polypropylene had a surface energy of 33 mJ/m 2. Oxidized polypropylene, after exposure to air at temperatures of 100 °C and 110 °C, had a range of maximum surface energies from 38 to 41 mJ/m 2. Comparisons between FTIR carbonyl peak growth and the surface energy showed that both methods detect oxidation, though the increase in surface energy is detected before the carbonyl peak growth is noticeable. The work of adhesion predicted by the surface free energies obtained in this work between a coated calcium carbonate and polypropylene changes by 10% due to the oxidation of the polymer at 110 °C.

Use of inverse gas chromatography to account for the pervaporation performance in the microemulsion breakdown

Mass transfer phenomenon that occurs in the pervaporation process when applied to the microemulsion breakdown, was confirmed by the results of inverse gas chromatography. The stationary phase for this study was polydimethylsiloxane (PDMS), a hydrophobic polymer employed as a membrane in the pervaporation technique. The retention times of the different molecule probes (toluene, cyclohexane, and n-butanol) gave an insight into the extent of the interactions between each of these molecules and the stationary phase; these molecules were the components of the two microemulsions in study. The infinite dilution conditions allowed to determine the thermodynamic and the chromatographic parameters γ ∞ (the infinite dilution activity coefficient), the Flory-Huggins parameter interactions χ 12 ∞ , and V g 0 (the specific retention volume), respectively. The magnitudes of the latter parameters threw some light on the permselectivity of the membrane in the pervaporation operation.

The use of inverse gas chromatography and gravimetric vapour sorption to study transitions in amorphous lactose

The aim of this study was to measure the glass transition of amorphous lactose under well-controlled temperature and humidity, using inverse gas chromatography (IGC) and to relate these data to gravimetric vapour sorption experiments. Amorphous lactose (spray-dried) was exposed to a stepwise increment in the relative humidity (%RH) under isothermal conditions in an IGC. At the end of each conditioning step a decane injection was made, and the retention volumes were calculated using the maximum peak height ( V max) method. The pressure drop across the column was recorded using the pressure transducers. These measurements were performed at various temperatures from 25 to 40 °C. The extent of water sorption at identical humidity (%RH) and temperature conditions was determined gravimetrically using dynamic vapour sorption (DVS). At each T, it was possible to determine: (1) a transition at low RH relating to the onset of mobility; (2) changes in retention volume relating to the point, where T g = T; (3) changes in pressure drop, which were related to the sample collapse. The rate and extent of water sorption was seen to alter at T g and also at a collapse point. Combinations of temperature and critical %RH (%cRH required to lower the dry glass transition temperature to the experimental temperature) obtained from IGC were comparable to those obtained from DVS. It was shown that at each T, the sample spontaneously crystallised, when T g was 32 °C below T. Inverse gas chromatograph can be used in this novel way to reveal the series of transitions that occur in amorphous materials.

Use of Inverse Gas Chromatography To Study Binary Polymer−Solvent Systems near the Glass Transition Temperature

A new model has been developed for inverse gas chromatography experiments for binary polymer-solvent systems. The model includes both bulk and surface effects and has been solved using the method of Laplace transforms. Retention data near the glass transition temperature were collected from the literature and correlated and predicted with the model. Frequently investigators estimate a polymer's glass transition temperature (Tg) from the Z-shaped retention data that often occur in this temperature range. The results presented here suggest that there is little or no correlation between the Z-shaped retention diagram and the glass transition temperature. New results are also presented on the origins of the Z-shaped retention diagram and on how a combination of bulk absorption, bulk diffusion, and surface adsorption contribute to it.

Letter to Editor: Use of Inverse Gas Chromatography (IGC) to Determine the Surface Energy and Surface Area of Powdered Materials

Letter to Editor: Use of Inverse Gas Chromatography (IGC) to Determine the Surface Energy and Surface Area of Powdered Materials

The use of inverse gas chromatography to assess the acid–base contributions to surface energies of cefditoren pivoxil and methacrylate copolymers and possible links to instability

It is known that acids and bases when mixed together have the potential to react, however, there is complexity when materials are in the solid state, as the surface of the solids may not have all functional groups of the molecule expressed in equal proportions. Conceptually a drug that is acidic when in solution could have a crystal surface that is largely basic (if the acid groups are aligned away from the surface). The interaction of cefditoren pivoxil (a basic drug when dissolved) and various Eudragit polymers was studied. The drug was chemically unstable with Eudragit EPO (basic) and stable with Eudragit L100 or S100 (both acidic). Thus, the hypothesis of this work was that the surface of these materials had a different nature to the dissolved molecules, such that solid state reactions do not proceed in line with the expectation from the solution state. Inverse phase gas chromatography (IGC) was used to investigate the cefditoren pivoxil and the Eudragits. The basic to acidic parameter ratios ( K D/ K A) on the powder surface of the samples by IGC revealed that surface nature was in keeping with the tendency to react, such that the incompatibility could be due to the acid–base interaction between any carbonyl groups having an amphoteric nature on the surface of cefditoren pivoxil crystal and dimethylaminoethyl groups having a basic nature on the powder surface of Eudragit EPO. This study indicated that IGC would be suitable to elucidate the cause of incompatibility between two different solids.