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Inverse Gas Chromatography (inverse + gas_chromatography)

Distribution by Scientific Domains

Polymers and Materials Science	50%

Selected Abstracts

Glass-Transition Temperature (Tg) of Free-Radically Prepared Polyacrylonitrile by Inverse Gas Chromatography, 1.

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 17 2002
A Study on Tg of Atactic Monodisperse Polystyrenes
Abstract The glass-transition temperature (Tg) of several atactic monodisperse polystyrenes (PSt)s was studied by an inverse gas chromatographic (IGC) analysis, as a preliminary study for the detection of the Tg of polyacrylonitrile. The Tg of PSt with different molecular weights was clearly obtained by this method. The agreement in the Tg values obtained by IGC and by differential scanning calorimetry (DSC) was quite good within the molecular-weight range Mp,=,7,600,2,430,000 (where, Mp,=,(Mn,×,Mw)1/2). This method has a wide universality for the detection of the Tg of polymers. Several essential factors were extracted for the establishment of the optimum conditions for IGC measurements, such as the concentration of polymer toward a clay matrix (10 wt.-%), and the type of lower probe, decane. The best probe was determined empirically from the most effective detection in the IGC measurements of PSt. Molecular-weight dependence of the Tg of PSt. Experimental data obtained here are indicated by an arrow. Other data was taken from ref.21 [source]

Glass-Transition Temperature (Tg) of Free-Radically Prepared Polyacrylonitrile by Inverse Gas Chromatography, 2,.

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 17 2002
Molecular-Weight Dependence of Tg of Two Different Types of Aqueous Polymers
Abstract The molecular-weight dependence of the glass-transition temperature (Tg) of a series of atactic polyacrylonitriles (PAN)s was studied by inverse gas chromatographic (IGC) analysis. PANs having different molecular weights were prepared by either; (i) the addition of isopropyl alcohol as a chain-transfer agent, or (ii) a scission reaction induced by the addition of alkali (NaOH) to a solution (N,N -dimethylformamide solution, at 25,°C) of the resulting polymer. The intrinsic viscosity [,] was in the range of 10.9,0.1 (dl,·,g,1), which corresponds to a viscosity-averaged molecular weight (Mv) of 1,590,000,3,000. As part of the results, a side reaction, which saw the conversion of the nitrile (CN) groups of PAN into amide (CONH2) and/or carboxylic acids (COOH) groups by alkali, was found to occur. The typical molecular-weight dependence of the Tg in free-radically prepared PAN was discussed in connection with a chain-transfer mechanism in an aqueous medium. Molecular-weight dependence of the Tg for PAN (WA). An error bar is given by a short vertical arrow. [source]

Analysis of the surface energy of pharmaceutical powders by inverse gas chromatography

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 2 2002
Ian M. Grimsey
Abstract The behavior of pharmaceutical solids, during either processing or use, can be noticeably affected by the surface energetics of the constituent particles. Several techniques exist to measure the surface energy, for example, sessile drop, and dynamic contact angle measurements. Inverse gas chromatography (IGC) is an alternative technique where the powder surface is characterized by the retention behavior of minute quantities of well-characterized vapors that are injected into a column containing the material of interest. Recently published articles using IGC on pharmaceutical powders have ranged from linking surface energetic data with triboelectric charging to studying the effect of surface moisture on surface energetics. Molecular modelling has also recently been used to explore the links between IGC data and the structural and chemical factors that influence surface properties, thereby achieving predictive knowledge regarding powder behavior during processing. In this minireview, the reported applications of IGC in the analysis of pharmaceutical powders are summarized and the major findings highlighted. © 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91:571,583, 2002 [source]

Lewis acid,base property of P(VDF- co -HFP) measured by inverse gas chromatography

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2008
Baoli Shi
Abstract Poly (vinylidene fluoride- co -hexafluoropropylene) P(VDF- co -HFP) is an excellent material for polymer electrolytes of lithium ion battery. To enhance the lithium ion transference number, some metal oxides were often embedded into P(VDF- co -HFP). The promising mechanism for the increase in lithium ionic conductivity was Lewis acid-base theory. In this experiment, the Lewis acid,base properties of P(VDF- co -HFP) were measured by inverse gas chromatography (IGC). The Lewis acid constant Ka of P(VDF- co -HFP) is 0.254, and the base constant Kb is 1.199. Compared with other polymers characterized by IGC, P(VDF- co -HFP) is the strongest Lewis basic polymers. Except aluminum ion, lithium ion is the strongest Lewis acidic ion according to their , value of Lewis acids. Therefore, a strong Lewis acid,base interaction will exist between lithium ion and P(VDF- co -HFP). This will restrict the transference of lithium ion in P(VDF- co -HFP). To enhance the lithium ion transference by blending other metal ions into P(VDF- co -HFP), it is suggested that the preferential ions should be Al3+, Mg2+, Na+, and Ca2+ because these metal ions have relative large , values. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Surface characterization of salmeterol xinafoate powders by inverse gas chromatography at finite coverage

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 3 2005
Henry H.Y. Tong
Abstract In our previous studies, surface analysis by inverse gas chromatography (IGC) at infinite dilution (zero coverage) was performed on four salmeterol xinafoate (SX) powdered samples, viz, two supercritical CO2 -processed Form I (SX-I) and Form II (SX-II) polymorphs, a commercial granulated SX (GSX) raw material and its micronized product (MSX). Both GSX and MSX are also of the same Form I polymorph. To further probe the differences in surface properties between the samples, the present study has extended the IGC analysis to the finite concentration range of selected energy probes. The adsorption isotherms of the SX samples were constructed using (nonpolar) octane, (polar acidic) chloroform, and (polar basic) tetrahydrofuran as liquid probes. Type II adsorption isotherms with weak knees were observed with each probe for all SX Form I samples. The extents of probe adsorption by the samples at various relative pressures follow the rank order: SX-II,>,GSX,,,MSX,>,SX-I, indicating that the SX-I has fewer high-energy adsorption sites than GSX and MSX. Type III isotherms were observed for SX-II with the two polar probes, indicative of weak adsorbate,adsorbent interactions. The additional information generated shows that IGC analysis at finite coverage is a valuable complementary tool to that at infinite dilution. © 2005 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 94:695,700, 2005 [source]