Inverse Gas Chromatography Method Research Articles

Assessment of the Thermodynamic Properties of DL-p-Mentha-1,8-diene, 4-Isopropyl-1-Methylcyclohexene (DL-limonene) by Inverse Gas Chromatography (IGC).

Limonene is a colorless liquid hydrocarbon and had been investigated as a plasticizer for many plastics. Prediction of solubility between different materials is an advantage in many ways, one of the most convenient ways to know the compatibility of materials is to determine the degree of solubility of them in each other. The concept of "solubility parameter" can help practitioners in this way.In this study, inverse gas chromatography (IGC) method at infinite dilution was used for determination of the thermodynamic properties of DL-p-mentha-1,8-diene, 4-Isopropyl-1-methylcyclohexene (DL-limonene). The interaction between DL-limonene and 13 solvents were examined in the temperature range of 63-123°C through the assessment of the thermodynamic sorption parameters, the parameters of mixing at infinite dilution, the weight fraction activity coefficient and the Flory-Huggins interaction parameters. Additionally, the solubility parameter for DL-limonene and the temperature dependence of these parameters was investigated as well.Results show that there is a temperature dependence in solubility parameter, which increases by decreasing temperature. However, there were no specific dependence between interaction parameters and temperature, but chemical structure appeared to have a significant effect on them as well as on the type and strength of intermolecular interactions between DL-limonene and investigated solvents. The solubility parameter δ2 of DL-limonene determined to be 19.20 (J/cm3)0.5 at 25°C.

Surface and Thermodynamic Characterizations and Secondary Transition of Novel Phthalocyanine Glass

The novel 4-(3-tert-butyl-4-hydroxyanisole)]phthalonitrile and its peripherally tetra substituted zinc phthalocyanine complex [2,9(10),16(17),23(24)-tetrakis(4-(3-tert-butyl-4-hydroxyanisole) phthalocyaninato]zinc(II) (ZnPc) were synthesized and characterized by elemental and spectroscopic analysis techniques. The inverse gas chromatography (IGC) method was used to obtain secondary transition, surface properties, and thermodynamic interaction parameters of the phthalocyanine glass. Phthalocyanine selectivity was investigated using the acetate and alcohol isomers by IGC method at temperatures between 313.2 and 423.2 K. The secondary transition temperature was obtained by IGC method and differential scanning calorimetry (DSC). The dispersive component of the surface free energy, γSD, of adsorbent surface was calculated in the infinite dilution region. The specific enthalpy of adsorption, ΔHAS, the specific free energy of adsorption, ΔGAS and the specific entropy of adsorption, ΔSAS of solvents on ZnPc were ...

The comparison of the three methods of specific surface evaluation – adsorptive porosimetry, inverse gas chromatography and mathematical method.

In the present study an attempt to determine the possibility of using novel measurement techniques for the evaluation of medical implants was made. The focus was put on the measurements of the specific surface area and associated characteristics of the knitted monofilament meshes made of polypropylene, used for the hernia treatment. As a part of examination, three methods of examination were compared - adsorptive porosimetry, inverse gas chromatography and mathematical method. The obtained results of the specific surface area confirmed the hypothesis stating that the results of specific surface area measurements depend on the applied measurement method.

Improving the wetting and dissolution of ibuprofen using solventless co-milling

The wetting and dissolution of a BCS class II drug (Ibuprofen) is enhanced by solventless solid dispersion technique using co-milling. The co-milling is performed in a planetary ball mill using 1:1wt. ratio of Ibuprofen (drug) and Microcrystalline cellulose, MCC (excipient). The improvement in wettability and dissolution after co-milling are compared with the raw ibuprofen, ball-milled ibuprofen without any excipient and v-blend mixture of ibuprofen with an excipient. The changes in crystal level properties and reduction in crystallinity due to co-milling are measured using Powder X-ray diffraction (P-XRD) and Differential Scanning Calorimetry (DSC) respectively. The increased interaction between ibuprofen and MCC as well as hydrogen bond formation is confirmed by Fourier Transform Infrared Spectroscopy (FTIR). The morphological changes are observed by optical microscopy and Field Emission Scanning Electron Microscopy (FESEM). The miscibility of drug and excipient and evidence of formation of glassy solutions are demonstrated by Modulated Temperature Differential Scanning Calorimetry (MTDSC) and Raman microscopy. The surface energy and wetting properties are determined using Inverse Gas Chromatography (IGC) and sessile drop method respectively. The results show that co-milling generates defects, strain, and reduction in crystallite size (changes in crystal level properties) which are responsible for the improvement of wetting and dissolution (96% in 90min). Also, with increase in co-milling time, the polar surface energy increases and the hydrophobic ibuprofen drug surface transforms into hydrophilic surface due to increase in OH groups of MCC on the ibuprofen surface. The present work quantified all the above-mentioned parameters including the acidic and basic parameters of co-milled ibuprofen using IGC. The technique improves the wetting and dissolution of hydrophobic drugs. It can be very well extended to BCS class II and IV drugs in the presence of different hydrophilic excipients.

Inverse gas chromatography as a method for determination of surface properties of binding materials

Inverse gas chromatography (IGC) is a promising measurement technique for investigating the surface properties of binding materials, which are the major influence element for the adsorption performance of superplasticizer. In this work, using the IGC method, blast furnace slag (BFS), sulphoaluminate cement (SAC) and portland cement (P·O) are employed to systematically evaluate the corresponding dispersive component (γsd), specific surface free energy (γsab), and acid-base properties. The obtained results show that γsd contributes to a major section of the surface free energy in the three binding materials, suggesting they are of a relatively low polarity. Compared to the two kinds of cements, the BFS possesses the highest dispersive and specific surface free energies (the values are 45.01 mJ/m2 and 11.68 mJ/m2, respectively), and also exhibits a wider distribution range of γsd, indicating their surfaces are heterogeneous. For acid-base properties, the results indicate the surfaces of three samples are basic in nature. In addition, the adsorption investigation shows that per unit surface of BFS adsorbs the most superplasticizer molecules, which indicates the higher surface free energies is beneficial to the superplasticizer adsorption.

Comparative study of surface properties determination of colored pearl-oyster-shell-derived filler using inverse gas chromatography method and contact angle measurements

Mollusk shells, such as clam, mussel, oyster and pearl oyster shells, are potential candidates for commercial calcium carbonate-based fillers. In this work, the surface properties of colored pearl-oyster-shell-derived filler (CMF) were investigated with comparison to those of pearl oyster shell powder (MSP), using an inverse gas chromatography (IGC) method and contact angle measurements. A developed computational model for the interpretation of surface free energy heterogeneity distributions was applied to both samples. The contact angle measurements revealed an amphiphilic nature. The dispersion component of surface free energy for both samples calculated using the Owens–Wendt–Kaelble (OWK), van Oss–Chaudhury–Good (vOCG) and Wu methods were consistent with those determined using the IGC method. The deconvolution of surface energetic sites confirmed their energetic heterogeneity. The CMF displayed lower work of cohesion, which could be beneficial to the fabrication of polymer composites, as typically reduced filler particle-particle interactions would result.

Crucial Role of Oxidation Debris of Carbon Nanotubes in Subsequent End-Use Applications of Carbon Nanotubes.

A facile purification method for oxidized carbon nanotubes (CNTs) is developed to preserve acidic carbon compounds (ACCs) for achieving high-quality dispersion of CNTs. The remaining ACCs, which originated from the surface destruction of CNTs during the oxidation process, are considered to play a crucial role in the dispersion of CNTs in water and various polar protic solvents. To elucidate the concrete role of ACCs, a direct titration method is applied to quantitatively investigate the degree of ionization of both CNTs and ACCs in their aqueous dispersions. While ACCs with strong carboxylic groups (pKa of around 2.9) are easily removed by the neutral or base washing of oxidized CNTs, which is common in the purification process, ACC-selective purification using acid washing preserves the ACCs attached to CNTs, thereby effectively stabilizing CNT dispersions in aqueous solutions. Additionally, the Hansen solubility parameters of ACC-preserved and ACC-removed CNTs were determined by the inverse gas chromatography method to estimate their miscibility in various solvents. The preserved ACCs significantly influenced the dispersibility of CNTs in polar protic solvents, which may widen the possible application of CNTs. Specifically, the ACC-preserved high-quality CNT dispersion produces high-performance CNT buckypaper with densely packed nanostructures. The Young's modulus and tensile strength of these buckypapers reach up to 12.0 and 91.0 MPa, respectively, which exceed those of ACC-removed CNTs in previous reports.

Surface free energy and mechanical performance of LDPE/CBF composites containing toxic-metal free filler

Heavy-metal contamination in children's toys is a widespread problem, and the international community has issued a series of safety standards to restrict and control the use of toxic metals in toys. In this work, a colored filler (CBF) was prepared using pearl oyster shell (POS) as the green raw material and azo dye as the colorant. Its surface properties were subsequently studied in comparison to those of POS powder using the inverse gas chromatography method. The dispersion surface free energy profiles for both CBF and POS showed that this component contributed the major part (>70%) to the total surface free energy. The CBF possessed lower polar surface free energy and was relatively more hydrophobic. It also showed a lower thermodynamic work of cohesion, allowing its better dispersion in a low density polyethylene (LDPE) matrix. Mechanical performance studies showed that adding CBF could significantly increase the tensile strength, elastic modulus, flexural strength and flexural modulus of LDPE composites. The absence of toxic metals coupled with excellent mechanical performance makes the CBF an ideal candidate as a filler for children's toys fabrication.

Enhanced Electrochemical Properties of Li3 VO4 with Controlled Oxygen Vacancies as Li-Ion Battery Anode.

Li3 VO4 , as a promising intercalation-type anode material for lithium-ion batteries, features a desired discharge potential (ca. 0.5-1.0 V vs. Li/Li+ ) and a good theoretical storage capacity (590 mAh g-1 with three Li+ inserted). However, the poor electrical conductivity of Li3 VO4 hinders its practical application. In the present work, various amounts of oxygen vacancies were introduced in Li3 VO4 through annealing in hydrogen to improve its conductivity. To elucidate the influence of oxygen vacancies on the electrochemical performances of Li3 VO4 , the surface energy of the resulting material was measured with an inverse gas chromatography method. It was found that Li3 VO4 annealed in pure hydrogen at 400 °C for 15 min exhibited a much higher surface energy (60.7 mJ m-2 ) than pristine Li3 VO4 (50.6 mJ m-2 ). The increased surface energy would lower the activation energy of phase transformation during the charge-discharge process, leading to improved electrochemical properties. As a result, the oxygen-deficient Li3 VO4 achieved a significantly improved specific capacity of 495 mAh g-1 at 0.1 Ag-1 (381 mAh g-1 for pristine Li3 VO4 ) and retains 165 mAh g-1 when the current density increases to 8 Ag-1 .

Preparation of Toluene-Imprinted Homogeneous Microspheres and Determination of Their Molecular Recognition Toward Template Vapor by Inverse Gas Chromatography

A toluene-imprinted polymers (MIPs) homogeneous microsphere was prepared by precipitation polymerization technique using toluene as porogen (also as template) with 4-vinyl pyridine (4-VP) as the functional monomer. Structural characterization was performed by the nitrogen adsorption method and optical microscope utilized for observing particle size of polymers. Retention capability and selectivity for this MIP toward template vapor and its relative compounds were evaluated and the isotherm rebinding capacity of the MIP tested by adopting an inverse gas chromatography method. Results indicated that the toluene-imprinted polymer (MIP3), as a stationary phase in gas chromatography, possessed high retention selectivity toward template vapor, with a retention factor value of 68.42, an imprinting factor value of 7.049, and selectivity factor values of 4.821 and 5.370 for the template relative to benzene and p-xylene, respectively. A model mixture containing toluene, benzene, and p-xylene could be effectively separated, with a resolution of 5.138 for toluene to p-xylene and of 1.762 for toluene to benzene. The isotherm adsorption curve for the MIP3 toward toluene vapor exhibited II type of BET adsorption. Additionally, the toluene-imprinted microspheres showed satisfactory applicability in the removal of toluene from polluted indoor air.

Effects of high surface energy on lithium-ion intercalation properties of Ni-doped Li3VO4

Nickel was doped into Li3VO4 (Ni-LVO) successfully via a facile room temperature reaction, and the resulting Ni-LVO nanocrystallites showed excellent lithium-ion storage properties with a capacity of 650 mAh g−1 at 50 mAh g−1 and excellent capacity stability as an anode in lithium-ion batteries, maintaining nearly 100% of the initial reversible capacity after 800 cycles at 1 A g−1. The superior electrochemical properties arose largely from the nickel doping in the Ni-LVO. The surface energy of the electrode material was analyzed by an inverse gas chromatography method, and the Ni-LVO surface energy, 43.91 mJ m−2, was much higher than the 30.74 mJ m−2 of Li3VO4. X-ray photoelectron spectra results demonstrated that nickel doping promoted the formation of tetravalent vanadium ions, V4+, as well as a more amorphous surface of Li3VO4, thus probably resulting in more nucleation sites for the phase transformation and reduced activation energy of the redox reactions and phase transition during the lithium-ion intercalation/extraction processes. Using nickel-doped nanocrystals boosts the stability and charge storage of rechargeable lithium-ion batteries, find scientists in China. Lithium and vanadium containing oxides, such as lithium vanadate (Li3VO4), could replace graphite anodes used in commercial lithium-ion batteries because they possess more stable crystal structure and offer greater energy storage. Guozhong Cao and colleagues at the National Center for Nanoscience and Technology have found how to make the switch to Li3VO4 anodes feasible by improving this materials' poor electrical conductivity. The researchers used a simple mixing procedure to introduce nickel atoms into the Li3VO4 framework and found that the resulting nanocrystals significantly enhanced battery performance. Characterization experiments revealed that these improvements arose from nickel's electrochemical and surface-disrupting effects: amorphous surface regions induced by the dopants likely resulted in additional nucleation sites for lithium-ion extraction and intercalation processes. Nickel doped Li3VO4 nanocrystallites with high surface energy showed excellent lithium ion storage property with a capacity of 650 mAh g−1 at 50 mAh g−1 and excellent capacity stability as anode in lithium ion batteries. The nickel doping promoted the formation of V4+ and more amorphous in the surface of Li3VO4, probably resulting in higher surface energy, more nucleation sites for the phase transformation and reducing the activation energy of the redox reactions and phase transition during the Li+ intercalation/extraction processes.

A novel colored talc filler: Preparation and surface property determination using two distinct methods

A better understanding of filler's surface properties is critical for determining the most effective polymer reinforcement fillers. In this work, a colored talc filler (CTF) was prepared and its surface properties were comparatively studied to those of talc filler (TF), using inverse gas chromatography (IGC) and contact angle methods—Owens–Wendt–Kaelble (OWK), van Oss–Chaudhury–Good (vOCG) and Wu. The results indicated that the dispersive component (γSD) for both samples contributed a major part (68–81%) of the total surface energy (γST), and displayed a decreasing trend with increasing surface coverage, meaning the fairly energetic surface heterogeneity for them. The γSD values determined by the contact angle methods were consistent, although lower than those using IGC analysis. The specific component (γSSP) calculated by the contact angle methods were also consistent and lower than those calculated using IGC. The specific Gibbs free energies of adsorption (ΔGsp) changed with surface coverages, further confirming the heterogeneous nature of both samples. The significantly lower γST value for CTF could reduce filler particle-particle interactions, allowing a better dispersion in matrix, and thus lead to an improvement in mechanical performance of CTF/polymer composite.

Evaluation of drug-carrier interactions in quaternary powder mixtures containing perindopril tert-butylamine and indapamide

Interactions occurring between components in the quaternary powder mixtures consisting of perindopril tert-butylamine, indapamide (active pharmaceutical ingredients), carrier substance and hydrophobic colloidal silica were examined. Two grades of lactose monohydrate: Spherolac® 100 and Granulac® 200 and two types of microcrystalline cellulose: M101D+ and Vivapur® 102 were used as carriers. We determined the size distribution (laser diffraction method), morphology (scanning electron microscopy) and a specific surface area of the powder particles (by nitrogen adsorption-desorption). For the determination of the surface energy of powder mixtures the method of inverse gas chromatography was applied. Investigated mixtures were characterized by surface parameters (dispersive component of surface energy, specific interactions parameters, specific surface area), work of adhesion and cohesion as well as Flory-Huggins parameter χ23'. Results obtained for all quaternary powder mixtures indicate existence of interactions between components. The strongest interactions occur for both blends with different types of microcrystalline cellulose (PM-1 and PM-4) while much weaker ones for powder mixtures with various types of lactose (PM-2 and PM-3).

Sorbtion and selective properties of supramolecular liquid crystal–β-cyclodextrin sorbent under conditions of gas chromatography

Sorbtion and selective properties of binary sorbent based on polar supramolecular (associated) liquid crystal (LC) 4-(3-hydroxypropyloxy)-4'-formylazobenzene (HPOFAB) and unsubstituted β-cyclodextrin are studied by the method of inverse gas chromatography. Standard thermodynamic functions of sorbtion in smectic phase A of the sorbent are determined for 21 organic compounds belonging to different classes of hydrocarbons and alcohols, which are compared to analogous functions obtained using a column with HPOFAB. The causes of decrease of retention of all studied compounds (excluding n-alkanes C9–C12) upon introduction of β-cyclodextrin into HPOFAB are discussed. It is established that mixed SA phase of the binary sorbent possess high values of para-meta-selectivity and enantioselectivity with respect to optical isomers of camphene.

Measurement of solubility thermodynamic and diffusion kinetic characteristic of solvents in PDMS by inverse gas chromatography

Inverse gas chromatography is a versatile and effective method for the characterization of the solubility thermodynamics and diffusion kinetic of solvent–polymer system with the advantages of fast, low dosage of samples and large range of temperature. Polydimethylsiloxane (PDMS) is well known as an excellent polymer membrane material for its high permeability to gases and liquids and widely used in the separation and purification of bio-fermentation broth which was mainly consisted by acetone, butanol, ethanol and water. In this paper, the inverse gas chromatography method was applied to measure solubility thermodynamics parameters like the infinite dilution activity coefficient and Flory–Huggins interaction parameter between those small molecules and PDMS. The infinite dilution diffusion coefficients were calculated by Van Deemter model over a temperature range of 373.2–413.2K. The diffusion coefficient was fitted with the temperature according to the Arrhenius correlation. The data could help the selection of membrane material in pervaporation or gas separation and the analysis of mass transfer process.

Thermodynamic and surface characterisation of 4-[4-((S)-citronellyloxy)benzoyloxy]benzoic acid thermotropic liquid crystal

ABSTRACTThe inverse gas chromatography (IGC) method was used to obtain thermodynamic and surface properties of the thermotropic liquid crystalline material, 4-[4-((S)-citronellyloxy)benzoyloxy]benzoic acid (CBB). Liquid crystal (LC) selectivity was investigated using the alcohol and acetate isomers by the IGC method at temperatures between 338.2 K and 463.2 K. The retention diagrams of n-decane, undecane, dodecane, tridecane, n-butyl acetate, iso-butyl acetate, ethylbenzene and chlorobenzene on CBB were plotted in the temperature range between 468.2 K and 493.2 K. The specific retention volume, , Flory–Huggins interaction parameter, , equation-of-state interaction parameter, , the partial molar heat of sorption, , the partial molar heat of mixing, , the molar heat of vaporization, and the weight fraction activity coefficient, , were determined.The dispersive component of the surface free energy, , of the studied adsorbent surface was estimated in the infinite dilution region. The specific free energy of adsorption, , the enthalpy of adsorption, and the entropy of adsorption, , of solvents on LC were determined. The values of were correlated with the donor and the acceptor numbers of the probes to quantify the acidic and the basic parameters of the LC surface. The values obtained for and parameters indicated an acidic character for the surface of CBB.

Surface properties of ZuMgAl hydrotalcite-like compounds by inverse gas chromatography

The structure of ZnMgAl hydrotalcite-like compounds (ZnMgAl-HTLC) prepared by hydrothermal synthesis was studied by X-ray diffraction (XRD). With a series of polar and nonpolar molecules as probes, inverse gas chromatography (IGC) was used to measure the surface properties of ZnMgAl-HTLC. It was found that the XRD pattern of ZnMgAl-HTLC was narrow, sharp and high. The results showed that ZnMgAl-HTLC with a higher purity was obtained by hydrothermal synthesis. The surface adsorption free energy was less than zero. The surface dispersive free energy was 6.02 mJ/m2. The acid-base interaction free energy was 5.33 kJ/mol. The adsorption enthalpy was 43.6 kJ/mol, and the adsorption entropy was 0.15 kJ/mol. The IGC method is significant in the study of the surface properties of ZnMgAl-HTLC.

Gas phase adsorption of alkanes, alkenes and aromatics on the sulfone-DUT-5 Metal Organic Framework

A sulfone functionalized DUT-5 Metal Organic Framework ‘SO2-DUT-5’ was synthesized using 4,4′-bibenzoic acid-2,2′-sulfone linkers. Its adsorption properties were studied and compared to those of the pristine DUT-5 material. The inverse gas chromatographic method was used to study the adsorption of C5–C7 linear, branched and cyclic alkanes, alkenes and aromatic molecules. SO2-DUT-5 shows shape-selective behaviour in the adsorption of linear, branched and iso-alkanes, whereas DUT-5 is non-selective. The presence of sulfone groups results in both a reduced pore size and more specific interaction sites, leading to the shape-selective behaviour towards linear alkanes and the slightly elevated preference for aromatic compounds in the low coverage area.The separation of n-hexane/benzene and 1-hexene/benzene mixtures at higher coverage was studied by performing breakthrough experiments at different temperatures and pressures. A remarkable change in selectivity is observed when the loading of the adsorbing molecules increases. At low degree of pore filling, no significant separation between n-hexane/benzene or 1-hexene/benzene occurs, while at higher loading separation becomes apparent with a preferential adsorption of benzene. This separation at high loading is a result of the more favourable packing of benzene in this unidimensional pore system.

Experimental Evaluation of the Adsorption, Diffusion, and Separation of CH4/N2 and CH4/CO2 Mixtures on Al-BDC MOF

Adsorption equilibrium, thermodynamics, and kinetics of CH4, N2, and CO2 were investigated by volumetric-chromatographic and inverse gas chromatographic (IGC) methods on the Al-BDC MOF. The binary adsorption data from the volumetric-chromatographic experiments represents that the Al-BDC MOF has a high CO2/CH4 selectivity ca. 11 and a CH4/N2 selectivity ca. 4.3 at 303 K, and appears to be a good candidate for the CH4 separation. The initial adsorption heats of CH4, N2, and CO2 on the Al-BDC MOF were determined to be 15.3, 11.5, and 32.2 kJmol−1 by IGC method, respectively. Moreover, the micropore diffusivities of N2, CH4 and CO2 in the Al-BDC MOF at 303 K were also estimated to be 1.58 × 10−7 cm2/s, 7.04 × 10−8 cm2/s, and 3.95 × 10−9 cm2/s, respectively. The results indicate that micropores play a crucial role in the adsorptive separation of the CH4/N2 and CH4/CO2 mixtures, and the IGC method is a validity manner to estimate the thermodynamic and kinetic parameters of MOF adsorbents.

Inverse gas chromatography for identification of poly(ethylene glycol adipate) and tripropionitrilamine on the surface of polymeric sorbent

Identification of the adsorption of poly(ethylene glycol adipate) (PEGA) and tripropionitrilamine (TPA) on styrene-divinylbenzene porous polymer was performed with the use of the inverse gas-chromatography method in finite concentration. PEGA and TPA were applied in quantities ω = 10−6−10−3 mass fractions. As test sorbates n-propanol, n-butanol, and n-hexane used. The adsorption isotherm and the values of specific retention volumes were calculated via the Glueckauf method. It was found that the dependence of the retention volumes on the sorbate concentration in gas phase of the studied samples is well approximated by a power function corresponding to the Freundlich isotherm. The possibility of detecting PEGA and TPA on the surface of sorbent through the A coefficients of a power function was shown, and a linear dependence between the A values and negative logarithm of ω was also found, making it possible to quantitatively determine TPA and PEGA on the surface of a sorbent.