Effects of solvent density on retention in gas–liquid chromatography: I. Alkanes solutes in polyethylene glycol stationary phases

• Published in: Journal of Chromatography A Vol. 953; no. 1; pp. 151 - 163
• Main Authors: GONZALEZ, F. R, PEREZ-PARAJON, J, GARCIA-DOMINGUEZ, J. A
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 12.04.2002; Elsevier
• Subjects: Alkanes; Alkanes - chemistry; Analytical chemistry; Chemistry; Chromatographic methods and physical methods associated with chromatography; Chromatography, Gas - methods; Exact sciences and technology; Gas chromatographic methods; Poly(ethylene glycol); Polyethylene Glycols - chemistry; Solubility; Solvents - chemistry; Thermodynamics; Gas chromatography; Poly(ethylene glycol); Thermodynamic parameters; Alkanes; Partition coefficients; Stationary phases, GC; Density; Hydrocarbon; Chromatographic retention; Enthalpy; Solubility; Partition coefficient; Entropy; Experimental study; Molecular weight property relation; Ethylene oxide polymer; Alkane; Gas liquid chromatography; Thermodynamic properties; Physicochemical properties; Stationary phase
• ISSN: 0021-9673
• DOI: 10.1016/S0021-9673(02)00162-0

Gas–liquid chromatographic columns were prepared coating silica capillaries with poly(oxyethylene) polymers of different molecular mass distributions, in the range of low number-average molar masses, where the density still varies significantly. A novel, high-temperature, rapid evaporation method was developed and applied to the static coating of the low-molecular-mass stationary phases. The analysis of alkanes retention data from these columns reveals that the dependence of the partition coefficient with the solvent macroscopic density is mainly due to a variation of entropy. Enthalpies of solute transfer contribute poorly to the observed variations of retention. Since the alkanes solubility diminishes with the increasing solvent density, and this variation is weakly dependent with temperature, it is concluded that the decrease of free-volume in the liquid is responsible for this behavior.