Inverse Gas Chromatography Method Research Articles

Time-resolved gas chromatography applied to submonolayer adsorption: Modeling and experimental approach

The reversed-flow inverse gas chromatographic method was used to study the local adsorption parameters of the action of five hydrocarbons on one hand, namely, ethane, ethene, ethyne, propene and 1-butene and of ozone, on the other, on two known and widely used oxides, CaO and SiO 2, respectively. Five physicochemical parameters concerning adsorption have been obtained for each of 20 heterogeneous systems studied, namely local adsorption energy, local adsorption isotherm, local monolayer capacity, probability density function for adsorption energies and energies from lateral interactions. Thus, the RF-IGC method is engaged to provide a new pathway for heterogeneous surface characterization, which is the basis of many scientific investigations and technological applications.

Characterization of fillers used in abrasive articles by means of inverse gas chromatography and principal component analysis

Abrasive articles consists of cutting particle—very often from electrocorundum, filler—inorganic compound, e.g. potassium fluoroborate or cryolite, binder—novolak resin and wetting agent—resol. The most important stages during manufacturing of grinding tools are: the coverage of the abrasive by wetting agent and proper hardening. The fillers play a very important role during the work of the grinding tools—they collect the heat and prevent the melting of resin. The surface properties of the components of grinding tools influence the interactions between them and the properties of the final product. Surface properties of different kinds of the fillers were examined by means of inverse gas chromatography (IGC). Dispersive component of the surface free energy γ S D at relative humidities: 30%, 60% and 90% and at various temperatures: 278, 283, 288 and 293 K was determined. It provided the data on stability of the fillers during their storage and/or weathering. The influence of the type of the filler on the hardening process by differential scanning calorimetry (DSC) was also studied. Principal component analysis (PCA) was applied to search the influence of the temperature and humidity onto the γ S D values for various fillers. This analysis showed that changes of the surface properties of fillers are significant at higher humidity close to 90%. Furthermore, PCA demonstrated that the type of filler does not influence meaningfully the hardening process. This approach has shown usefulness of IGC and calorimetric methods in studying the properties of abrasive articles as well as PCA in the interpretation of physicochemical characteristics of abrasive materials.

Determination of thermodynamic and transport properties of solvents and non solvents in poly(L‐lactide‐co‐glycolide)

AbstractThermodynamic properties, partition coefficient, and diffusion coefficients of the various solvents (acetone, dichloromethane, trichloromethane, ethyl acetate, ethyl alcohol, tetrahydrofuran, and water) in poly(lactide‐co‐glycolide) (PLGA) at infinite dilution of the solvent have been determined by inverse gas chromatography (IGC). In IGC method, which is based on the characteristic equilibrium partitioning of a solute between a mobile phase and a stationary phase, a small pulse of solvent is introduced into the column and by the aid of retention volume of the solvent, several polymer solvent interaction properties, namely retention volume (Vg), infinitely dilute weight fraction activity coefficient (Ω), Flory–Huggins interaction parameter (χ), and solubility parameters of the polymer (δ) can be determined. The thermodynamic results indicated that trichloromethane and dichloromethane were the most suitable solvents among all the solvents studied for PLGA. The partition (K) and diffusion coefficients (Dp) of various solvents at infinite dilution of the solvent were calculated by using the model developed by Pawlisch et al. (Macromolecules 1987, 20, 1564). The optimum K and Dp values that best fit the data were found and the model predicted experimental data very well. So IGC method is a powerful tool for the determination of thermodynamic and diffusion properties of solvent in polymer at infinite dilution of the solvent. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2426–2432, 2006

Time distribution of adsorption entropy of gases on heterogeneous surfaces by reversed-flow gas chromatography

The reversed-flow gas chromatography (RF-GC) technique has been applied to measure the adsorption entropy over time, when gaseous pentane is adsorbed on the surface of two solids (γ-alumina and a silica supported rhodium catalyst) at 393.15 and 413.15 K, respectively. Utilizing experimental chromatographic data, this novel methodology also permits the simultaneous measurement of the local adsorption energy, ɛ, local equilibrium adsorbed concentration, c s * , and local adsorption isotherm, θ( p, T, ɛ) in a time resolved way. In contrast with other inverse gas chromatographic methods, which determine the standard entropy at zero surface coverage, the present method operates over a wide range of surface coverage taking into account not only the adsorbate–adsorbent interaction, but also the adsorbate–adsorbate interaction. One of the most interesting observations of the present work is the fact that the interaction of n-pentane is spontaneous on the Rh/SiO 2 catalyst for a very short time interval compared to that on γ-Al 2O 3. This can explain the different kinetic behavior of each particular gas–solid system, and it can be attributed to the fact that large amounts of n-C 5H 12 are present on the active sites of the Rh/SiO 2 catalyst compared to those on γ-Al 2O 3, as the local equilibrium adsorbed concentration values, c s * , indicate.

Synthesis, characterization, and thermodynamic properties of poly(3‐mesityl‐2‐hydroxypropyl methacrylate)

AbstractPoly(3‐mesityl‐2‐hydroxypropyl methacrylate) (PMHPMA) was synthesized in a 1,4‐dioxane solution with 2,2′‐azobisisobutyronitrile as the initiator at 60°C. The homopolymer and its monomer were characterized with 1H‐ and 13C‐NMR, Fourier transform infrared, differential scanning calorimetry, thermogravimetric analysis, size exclusion chromatography, and elemental analysis techniques. According to size exclusion chromatography analysis, the number‐average molecular weight, weight‐average molecular weight, and polydispersity index of PMHPMA were 65,864 g/mol, 215,375 g/mol, and 3.275, respectively. According to thermogravimetric analysis, the carbonaceous residue value of PMHPMA was 14% at 500°C. The values of the specific retention volume, adsorption enthalpy, sorption enthalpy, sorption free energy, sorption entropy, partial molar free energy, partial molar heat of mixing, weight fraction activity coefficient of solute probes at infinite dilution (Ω), and Flory–Huggins interaction parameter (χ) were calculated for the interactions of PMHPMA with selected alcohols and alkanes by the inverse gas chromatography method at various temperatures. According to Ω and χ, selected alcohols and alkanes were nonsolvents for PMHPMA at 423–453 K. Also, the solubility parameter of PMHPMA (δ2) was found to be 24.24 and 26.33 (J/cm3)0.5 from the slope and intercept of (δ/RT) − χ/V1 = (2δ2/RT)δ1 − δ/RT at 443 K, respectively [where δ1 is the solubility parameter of the probe, V1 is the molar volume of the solute, T is the column temperature (K), and R is the universal gas constant]. The glass‐transition temperature of PMHPMA was found to be 386 and 385 K by inverse gas chromatography and differential scanning calorimetry techniques, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 101–109, 2006

Charakterystyka warstwy wierzchniej wybranych cementow glasjonomerowych metoda odwroconej chromatografii gazowej w warunkach zwiekszonej wilgotnosci

Theoretical fundamentals of inverse gas chromatography (IGC) method applied to evaluation of surface properties of various materials, especially glass-ionomer cements as the subjects of investigations, were presented. The values of dispersive component of surface free energy (γ d s ) of two such cements, used as the dental fillings, were determined by IGC (Table 1). The following parameters, except of the cement type, were investigated: relative humidity of carrier gas used in IGC method (RH = 60 or 80 %), type of medium for the sample storage before the measurements (water or artificial saliva) and storage time (up to 180 days). RH value appeared to be the most important parameter: at lower humidity of a carrier gas the surface activity of cements has usually been greater. Unambiguous determination of the effects of another parameters appeared to be impossible because of non-directed fluctuations of γ d s values. The results obtained suggest similar surface activity of both fillings.

Thermodynamics of Sorption in an Amorphous Perfluorinated Rubber Studied by Inverse Gas Chromatography

The work is aimed to further investigate thermodynamics of sorption of organic vapors in perfluorinated polymers. Amorphous perfluorinated random copolymer of 50.7 mol % tetrafluoroethylene and 49.3 mol % perfluoromethylvinyl ether, poly(TFE−PMVE), was studied using the inverse gas chromatography method. As solutes, several hydrocarbons and fluorocarbons of different classes were studied, namely, n-alkanes C7−C10, benzene and toluene, methylcyclohexane, n-perfluoroalkanes C6 and C8, perfluoromethylcyclohexane, perfluorinated benzene, and toluene. In addition, partially fluorinated toluene derivatives were investigated. It was shown that solubility coefficients S of fluorocarbons in this rubbery polymer are significantly higher than those of their hydrocarbon analogues. Correlations of the type ln S = A + BTc2, where Tc is the critical temperature of the solutes, were demonstrated for both hydrocarbons and fluorocarbons; however, the curve for fluorocarbons is located above that of hydrocarbons. Therefore, in this regard, the behavior of perfluorinated rubber is analogous to the amorphous glassy perfluorinated polymers studied earlier. Hydrocarbons and fluorocarbons also reveal significant differences in other thermodynamic parameters of sorption in poly(TFE−PMVE): enthalpies of sorption, activity coefficients, partial molar enthalpies of mixing, and Flory−Huggins parameters.

Synthesis, characterization and thermodynamic properties of poly(3-mesityl-2-hydroxypropyl methacrylate- co- N-vinyl-2-pyrrolidone)

Poly(3-mesityl-2-hydroxypropyl methacrylate- co- N-vinyl-2-pyrrolidone) P(MHPMA- co-VP) was synthesized in 1, 4-dioxane solution using benzoyl peroxide (BPO) as initiator at 60 °C. The copolymer was characterized by 1H 13C NMR, FT-IR, DSC, TGA, size exclusion chromatography analysis (SEC) and elemental analysis techniques. According to SEC, the number-average molecular weight ( M n), weight-average molecular weight ( M w) and polydispersity index (PDI) values of PMHPMA- co-VP were found to be 58,000, 481,000 g/mol and 8.26, respectively. According to TGA, carbonaceous residue value of PMHPMA- co-VP was found to be 6% at 500 °C. Also, some thermodynamic properties of PMHPMA- co-VP such as the adsorption enthalpy, Δ H a, molar evaporation enthalpy, Δ H v, the sorption enthalpy, Δ H 1 s , sorption free energy, Δ G 1 s , sorption entropy, Δ S 1 s , the partial molar free energy, Δ G 1 ∞ , the partial molar heat of mixing, Δ H 1 ∞ , at infinite dilution was determined for the interactions of PMHPMA- co-VP with selected alcohols and alkanes by inverse gas chromatography (IGC) method in the temperature range of 323–463 K. According to the specific retention volumes, V g 0 , the weight fraction activity coefficients of solute probes at infinite dilution, Ω 1 ∞ , and Flory–Huggins interaction parameters, χ 12 ∞ between PMHPMA- co-VP-solvents were determined in 413–453 K. According to Ω 1 ∞ and χ 12 ∞ , selected alcohols and alkanes were found to be non-solvent for PMHPMA- co-VP at 413–453 K. The glass transition temperature, T g, of the PMHPMA- co-VP found to be 370 and 363 K, respectively, by IGC and DSC techniques, respectively.

Characterization of Environmentally Friendly Polymers by Inverse Gas Chromatography: I Amylopectin

Amylopectin, as a potato starch based polymer, with a molecular weight of six million gram/mol was characterized using the Inverse Gas Chromatography Method (IGC). DSC method was also used to measure the glass and melting temperatures. Both DSC and IGC agreed well on a Tg of 105°C and Tm of 160–166°C. Nineteen solutes (solvents) were injected onto a chromatographic column containing amylopectin. These solutes revealed the interaction of alkanes with AP, and the wettability and water intake of AP. Alkanes showed exothermic values of interaction parameters which were increased as the temperature increased and as the number of carbons in the alkane series decreased. Retention diagrams of these solutes in a temperature range of 80–200°C revealed two zones, crystalline and amorphous. Tg and Tm were measured using these zones which complimented the DSC values. The two zones were used to calculate the degree of crystallinity below the melting temperature which ranged from 85% at 104°C to 0% at 161°C. The dispersive component of the surface energy of amylopectin was measured using alkanes which ranged from 25.35 mJ/m2 at 80°C to 8.47 mJ/m2 at 200°C. This is attributed to the weak crystalline surface of AP at 80°C and when the surface melted at 160°C the surface energy decreased due to the thermal expansion of the surface.

Determination of the Henry Constant for Zeolite-VOC Systems Using Massic and Chromatographic Adsorption Data

Both the inverse gas chromatographic method and the dynamic gravimetric-calorimetric method were tested in order to determine the Henry constant for toluene on a Na-faujasite type zeolite. We used the pulse technique for the chromatographic method and a system generating low concentration of VOC in a helium flow for the gravimetric technique. The experimental determinations of the Henry constants for toluene were achieved in two different temperature ranges (from 363 to 548 K for gravimetry and from 548 to 673 K for chromatography). The results presented in this paper show the complementarity of two different techniques for the Henry constants determination. The Henry constants obtained with the two techniques at 548 K differ from 8%.

Investigation of Thermodynamic Properties of PIBMA-PVC (50%/50%) and P-4-t-BS-PVC (50%/50%) Blends Systems by Inverse Gas Chromatography

ABSTRACT The specific retention volumes, , values of the poly (isobutyl methacrylate)-poly (vinyl chloride) (PIBMA-PVC) (50%/50%) and poly (-4-tert-butyl styrene)-poly (vinyl chloride) (P-4-t-BS-PVC) (50%/50%) blends-probe systems were calculated between 383 and 423 K by inverse gas chromatography technique. According to these data, the thermodynamic properties such as the sorption enthalpy (), sorption free energy (), sorption entropy (), the partial molar free energy (), and the partial molar heat of mixing, () at infinite dilution were determined for the interactions of (PIBMA-PVC) (50%/50%) and (P-4-t-BS-PVC) (50%/50%) blends with alcohols and aromatics and CHCl3 by inverse gas chromatography method in the temperature range of 383–423 K. The sorption values and values were observed to be exothermic, and , , and values were observed to be endothermic. The values of PIBMA-PVC (50%/50%) and P (-4-t-BS)-PVC (50%/50%) blends-alcohols systems changed from 9.73 to 18.17 kJ/mol and from 10.00 to 16.83 kJ/mol, respectively. Flory-Huggins interaction parameters, χ12, χ13, χ14, χ1(23) and χ1(24) values of PVC, PIBMA, P (4-t-BS), PIBMA-PVC (50%/50%) and P (-4-t-BS)-PVC (50%/50%) blend systems were determined at 413–423 K. In addition, χ23′ and χ24′ values of alcohols changed from 1.191 to 2.473 and from 1.342 to 1.839 for PIBMA-PVC (50%/50%) and P (-4-t-BS)-PVC (50%/50%) blends, respectively, at 413 K.

Adsorption of n‐Alkanes on Silicon Nitride Nanopowder

Adsorption properties of silicon nitride beads were investigated by the inverse gas chromatography (IGC) method. Silicon nitride beads were obtained from a commercial nanopowder. Retentions of n‐pentane, n‐hexane, n‐heptane, and n‐octane were measured in the temperature range from 343 to 383 K, at zero surface coverage. Surface partition coefficients and the related thermodynamic functions (standard free energy changes, standard state enthalpy, and entropy changes) of the adsorption process were determined. The dispersive component of the surface free energy of silicon nitride, at investigated temperatures, was also calculated.

Quantitative Study of the Adsorption of Aromatic Hydrocarbons (Benzene, Toluene, and p-Xylene) on Dealuminated Clinoptilolites

Adsorption of benzene, toluene, and p-xylene (BTX) on dealuminated clinoptilolites was investigated in the temperature range of 398−498 K by way of the inverse gas chromatography method. The dealuminated zeolites were prepared via a chosen number of acid treatments of natural clinoptilolite precursors with aqueous HCl. Both natural and acid-leached substrates were characterized by X-ray diffraction, N2 adsorption at 76 K, and BTX adsorption. The Freundlich, Langmuir, and Dubinin−Astakhov adsorption models were found to approximately fit the BTX adsorption data, within the selected temperature range. The uptake degree of these aromatic hydrocarbons was temperature-dependent. Additionally, the degree of interaction between these BTX vapors and the dealuminated clinoptilolite samples was examined through the evaluation of the isosteric heat of adsorption by employing the Clausius−Clapeyron equation.

Determination of thermodynamic properties of isotactic poly(1-butene) at infinite dilution using density and inverse gas chromatography

The partial molar volumes, V 1 M , and the molar volume of isotactic crystalline low-molecular-weight poly(1-butene), iPBu-1, V 1, have been calculated from the measured density of {iPBu-1 + solvent ( n-hexane, n-heptane, n-nonane, n-decane, p-xylene, cyclohexane and chloroform)} systems. Some of the thermodynamic quantities were also obtained for the iPBu-1 with eight hydrocarbons ( n-octane, n-decane, n-undecane, n-dodecane, n-tridecane, o-xylene, m-xylene, p-xylene) by the method of inverse gas chromatography at various temperatures. The weight fraction activity coefficients of the solvent at infinite dilution, Ω 2 ∞ , and the Flory-Huggins thermodynamic interaction parameters, χ 21 ∞ , between polymer and solvents were determined. The partial molar free energy, Δ G 2 ∞ , the partial molar heat of mixing, Δ H 2 ∞ , at infinite dilution and the polymer solubility parameter, δ 1, were calculated. Additionally, the (solid + liquid) binary mixtures equilibria, SLE, of iPBu-1 with three hydrocarbons ( n-octane, n-decane and m-xylene) were studied by a dynamic method. By performing these experiments over a large concentration range, the T– x phase diagrams of the polymer–solvent systems were constructed. The excess Gibbs energy models were used to describe the nonideal behaviour of the liquid phase. The Ω 2 ∞ were determined from the solubility measurements and were predicted by using the UNIFAC FV model.

Determination of Poly[(2-Phenyl-1,3- dioxolane-4-yl) Methyl Methacrylate-co- glycidyl Methacrylate]-Probe Interactions by Inverse Gas Chromatography

In this study, we determined the thermodynamic properties [such as the adsorption enthalpy, ΔH a , the sorption enthalpy, , sorption free energy, , sorption entropy, , the partial molar free energy, , and the partial molar heat of mixing ] at infinite dilution for the interactions of poly[(2-phenyl-1,3-dioxolane-4-yl) methyl methacrylate-co-glycidyl methacrylate] poly (PDMMA-co-GMA) with alcohols and n-alkanes by the inverse gas chromatography method in the temperature range of 343–463K. According to the specific retention volumes (), the weight fraction activity coefficients of solute probes at infinite dilution, Ω1 ∞, and Flory-Huggins interaction parameters (χ ∞ 12) between poly (PDMMA-co-GMA)-solvents were determined in 423–463K. According to and , selected alcohols and n-alkanes were found to be nonsolvent for poly (PDMMA-co-GMA) between 423 and 463K. Also, the solubility parameters, δ 2, of poly (PDMMA-co-GMA) were found to be 22.15 (J cm−3)0.5 and 25.50 (J cm−3)0.5 from slope and intercept of [(/RT) − /V 1) = (2δ 2/RT)δ 1 − /RT equation, at 443K, respectively. The glass transition temperature (T g ) of the poly (PDMMA-co-GMA) was found to be 370 and 367K, respectively, by inverse gas chromatography and differential scanning colorimetry (DSC) techniques.

Determination of Rate of Crystallinity and Thermodynamical Interaction Parameters of Polycaprolactone with Some Solvents by Gas Chromatography

AbstractThe retention diagram of polycaprolactone for tert‐butyl acetate was obtained by inverse gas chromatography method in the temperature range of 40‐140 °C. Rate of crystallinity was determined between 45.0 percent and 37.1 percent in the temperatures at 40 and 53 °C, respectively. Thermodynamic interaction parameters were determined for cyclopentane, cyclohexane, tetrahydrofuran and 1,4‐dioxane with polycaprolactone between 70 and 130 °C. Specific retention volumes, Vgo, Flory Huggins polymer‐solvent interaction parameters, χ12∞, equation of state polymer‐solvent interaction parameters, χ12*, weight fraction activity coefficients of the solvents at infinite dilution, Ω1∞, effective exchange energy parameters, X̄12were determined.

Inverse gas chromatographic method for measurement of interactions between soy protein isolate and selected flavor compounds under controlled relative humidity.

An inverse gas chromatographic (IGC) method was developed to study the binding interactions between selected volatile flavor compounds and soy protein isolate (SPI) under controlled relative humidity (RH). Three volatile probes (hexane, 1-hexanol, and hexanal) at very low levels were used to evaluate and validate system performance. On the basis of the thermodynamic data and the isotherms measured at 0% RH, 1-hexanol and hexanal had higher binding affinities than hexane, which could be attributed to hydrogen-bonding interactions with SPI. At 30% RH, 1-hexanol and hexanal were retained less than at 0% RH, indicating possible competition for binding sites on the SPI surface between water and volatile probe molecules. Results showed that the thermodynamic data determined were comparable to the available literature values. Use of IGC allowed for the rapid and precise generation of sorption isotherms. Repeatability between replicate injections and reproducibility across columns were very good. IGC is a potentially high-throughput method for the sensitive, precise, and accurate measurement of flavor-ingredient interactions in low-moisture food systems.

Thermodynamic Interaction Parameters of Tetra-n-undecylcalix[4]resorcinarenes with Selected Solvents Studied by Inverse Gas Chromatography

The basic thermodynamic parameters, characterising intermolecular interactions of tetra-n-undecylcalix[4]resorcinarene and its octaacetate derivative with simple organic solutes, were calculated by using the inverse gas chromatography method. Free energy, enthalpy and entropy of sorption were determined.

Concentration dependency of interaction parameter between PVC and plasticizers using inverse gas chromatography

AbstractThe inverse gas chromatography method was extended to study the concentration dependent Flory–Huggins interaction parameter between poly(vinyl chloride) (PVC) and plasticizers using literature data. For both PVC/polyadipate and PVC/epoxidized soybean oil (ESO) systems, the miscibility was better at the high PVC end. The specific interaction between PVC and plasticizers was estimated from the difference between the experimental results and the enthalpies of mixing predicted by the solubility parameter model. The interaction was negative and skewed toward the high PVC end, and rendered the overall interaction parameter negative at high PVC compositions. Chemical potential was used to determine the phase composition of PVC/plasticizer mixtures. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 146–156, 2004

129Xe-NMR study of free volume in amorphous perfluorinated polymers: comparsion with other methods

The 129Xe-NMR method was used for evaluation of the sizes of free volume elements in amorphous glassy materials—random copolymers of tetrafluoroethylene and perfluorodioxoles of different structures. 129Xe chemical shifts were measured at different pressures up to 1060 Torr. The zero pressure chemical shifts obtained by extrapolation were used for calculation of the diameters of microcavities having spherical and cylindrical shapes. The sizes of microcavities are consistent with those found by means of positron annihilation lifetimes and inverse gas chromatography methods.