Chromatography and Analytical Techniques

Biography

Biography: Tayssir hamieh

Abstract

The inverse gas chromatography (IGC) technique at infinite dilution was used during the last forty years to determine the surface physicochemical properties, the Lewis acid-base constants as well as the London dispersive surface free energy 𝜸𝒔 𝒅 of materials and nanomaterials. In this study, we give a new and complete methodology to study the surfaces and interfaces of materials by criticizing the classic chromatographic models and by proposing new models that give more accurate results. While the London dispersive surface free energy was estimated by using the well-known Fowkes equation, Dorris-Gray relation, we proposed a correction to this relation and testing six other molecular models based on the values of the surface areas of organic molecules and Hamieh model taking into account the thermal effect. We determinednewexpressions of the various surface area, respectively,of n-alkanes 𝑎(𝑛, 𝑇), methylene group 𝑎−𝐶𝐻2− and polar molecules 𝑎𝑋(𝑇) versus the temperature T and using the new expressions to obtain more precise values of the surface parameters of materials. The Gibbs surface free energy of the adsorption values obtained by inverse gas chromatography against the temperature was determined for many surfaces by using fourteen methods such as that of Swayer-Brookman, Saint-Flour Papirer, Donnet, Brendlé and Papirer, Chehimi et al, Hamieh methods (thermal method and the methods of the enthalpy of vaporization as a function of the temperature ∆𝑯𝒗𝒂𝒑 𝟎 (𝑻) and the standard enthalpy of formation ∆𝑯𝒇 𝟎 and the six molecular models. The Lewis acidity parameter 𝑲𝑨 and Lewis basicity parameter, 𝑲𝑫 was calculated by the above stated fourteen methods. Our results based on the new concepts and models gave the more accurate values of the specific surface thermodynamic variables of materials compared to the other inverse gas chromatography methods.