Free Energy of Adsorption and Separation in Ultra-short Gas Solid Chromatographic Column

Abstract

Gas solid chromatography (GSC) has been widely used for separation of permanent gases and small organic compounds. For larger organic compounds, their free energies of adsorption are very high. Therefore, very high temperature or very long time is required to elute these compounds out of the GSC column. This is the major drawback of GSC. When the standard free energy of adsorption was subdivided into two parts, the free energy contributed from the funcional group(ΔG₀) and the free energy contributed from the methylene group(δG), it is found that δG is very high (-0.549 Kcal/carbon atom) while the δG of BP1 column is only -0.332 Kcal/carbon atm. The high value of δG is considered to be advantageous that larger organic compounds can be separated on a short or ultra-short column. Normal alkanes (C₁₂-C₁₈) and fatty alcohols (C₂₂-C₃₄) from rice bran wax are used as models fpr the separations on an ultra-short (20cm) GSC column.

Keywords : Gas Solid Capillary Columns / Column Length / Thermodynamic Potential