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Inverse gas chromatography is a physical characterization technique that is used in the analysis of the surfaces of solids. Traditional GC is an analytical technique. Inverse gas chromatography or IGC is a highly sensitive and versatile gas phase technique developed over 40 years ago to study the surface and bulk properties of particulate and fibrous materials. In IGC the roles of the stationary (solid) and mobile (gas or vapor) phases are inverted from traditional analytical gas chromatography (GC). In GC, a standard column is used to separate and characterize several gases and/or vapors. In IGC, a single gas or vapor (probe molecule) is injected into a column packed with the solid sample under investigation. Instead of an analytical technique, IGC is considered a materials characterization technique. During an IGC experiment a pulse or constant concentration of a known gas or vapor (probe molecule) is injected down the column at a fixed carrier gas flow rate. The retention time of the probe molecule is then measured by traditional GC detectors (i.e. flame ionization detector or thermal conductivity detector). Measuring how the retention time changes as a function of probe molecule chemistry, probe molecule size, probe molecule concentration, column temperature, or carrier gas flow rate can elucidate a wide range of physic-chemical properties of the solid under investigation. Several in depth reviews of IGC have been published previously.〔J. Condor and C. Young, Physicochemical measurement by gas chromatography, John Wiley and Sons, Chichester, UK (1979)〕〔F. Thielmann, Journal of Chromatography A. 1037 (2004) 115.〕 IGC experiments are typically carried out at infinite dilution where only small amounts of probe molecule are injected. This region is also called Henry's law region or linear region of the sorption isotherm. At infinite dilution probe-probe interactions are assumed negligible and any retention is only due to probe-solid interactions. The resulting retention volume, ''V''''R''o, is given by the following equation: : where ''j'' is the James–Martin pressure drop correction, ''m'' is the sample mass, ''F'' is the carrier gas flow rate at standard temperature and pressure, ''t''''R'' is the gross retention time for the injected probe, ''t''o is the retention time for a non-interaction probe (i.e. dead-time), and ''T'' is the absolute temperature. ==Surface energy determination== The main application of IGC is to measure the surface energy of solids (fibers, particulates, and films). Surface energy is defined as the amount of energy required to create a unit area of a solid surface; analogous to surface tension of a liquid. Also, the surface energy can be defined as the excess energy at the surface of a material compared to the bulk. The surface energy (γ) is directly related to the thermodynamic work of adhesion (''W''adh) between two materials as given by the following equation: : where 1 and 2 represent the two components in the composite or blend. When determining if two materials will adhere it is common to compare the work of adhesion with the work of cohesion, ''W''coh = 2''γ''. If the work of adhesion is greater than the work of cohesion, then the two materials are thermodynamically favored to adhere. Surface energies are commonly measured by contact angle methods. However, these methods are ideally designed for flat, uniform surfaces. For contact angle measurements on powders, they are typically compressed or adhered to a substrate which can effectively change the surface characteristics of the powder. Alternatively, the Washburn method can be used, but this has been shown to be affected by column packing, particle size, and pore geometry.〔J. Dove, G. Buckton, and C. Doherty, International Journal of Pharmaceutics. 138 (1996) 199–206.〕 IGC is a gas phase technique, thus is not subject to the above limitations of the liquid phase techniques. To measure the solid surface energy by IGC a series of injections using different probe molecules is performed at defined column conditions. It is possible to ascertain both the dispersive component of the surface energy and acid-base properties via IGC. For the dispersive surface energy, the retention volumes for a series of n-alkane vapors (i.e. decane, nonane, octane, heptanes, etc.) are measured. The Dorris and Gray.〔G.M. Doris and D.G. Gray, Journal of Colloids and Interfacial Science. 56 (1964) 353.〕 or Schultz 〔J. Schultz, L. Lavielle, and C. Martin, Journal of Adhesion. 77 (1980) 353–362.〕 methods can then be used to calculate the dispersive surface energy. Retention volumes for polar probes (i.e. toluene, ethyl acetate, acetone, ethanol, acetonitrile, chloroform, dichloromethane, etc.) can then be used to determine the acid-base characteristics of the solid using either the Gutmann,〔V. Gutmann, Coordination Chemistry Reviews. 2 (1966) 239–256.〕 or Good-van Oss theory.〔C.J. van Oss, R.J. Good, and M.K. Chaudhury, Langmuir. 4 (1988) 884–891.〕 Other parameters accessible by IGC include: heats of sorption (), adsorption isotherms,〔E. Cremer and H. Huber, 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Inverse gas chromatography」の詳細全文を読む スポンサード リンク
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