Investigation of Retention Process in Capillary Gas Liquid Chromatography
毛细管气液色谱保留过程的研究

Fused silica capillary column was used to examine the mechanism by which solutes are retained in gas liquid chromatography so as to eliminate the disturbance from support used in packed column. An equation was derived to correlate capacity factor with equilibrium constants in process of partition between gas liquid phases (K L) and adsorption on gas liquid interface (K GL ) and parameters of column from original equation by Martin in packed column. In this work PEG 20M was used to prepare columns with different thickness of liquid film and on these columns the capacity factors of 29 solutes belonging to various classes were determined at nine temperatures. The obvious interfacial adsorption was observed especially when low phase loading column and low column temperature used. To examine the characteristics of interfacial adsorption the correlation of lnK GL with carbon number for three homologous series and with temperature were achieved. Authors found that the enthalpy in interfacial adsorption is higher than that in partition, especially for n alkanes and lnK GL can be linearly correlated with boiling point and lnK L. Consequently, authors believe that the molecular interaction on gas liquid interface is a mixed one from solute solvent and solute solute. Therefore, interfacial adsorption cannot be significantly decreased through the increase of column temperature when solute solvent interaction is similar to solute solute one. The data of lnK GL and lnK L at the boiling point of solute given by interpolation or extrapolation showed that the difference of them have nothing to do with the properties of solute.