35-9/Olesik.../High-Performance Size Exclusion Chromatography....

Published: Journal of Chromatographic Science, Volume 35, Number 9, September 1997, pp. 409–416.

High-Performance Size Exclusion Chromatography Using Enhanced-Fluidity Liquid Mobile Phases
H. Yuan, I. Souvignet, and S.V. Olesik

One of the most effective ways to improve the resolution of size exclusion chromatography (SEC) is to decrease band broadening by lowering the mobile phase viscosity. In this study, the use of enhanced-fluidity liquid mixtures of tetrahydrofuran (THF)–liquid CO₂ for the separation of polystyrene standards by SEC under room temperature and moderate pressure conditions was investigated. By adding low viscosity liquid CO₂ to THF, the mixtures had markedly lower viscosities than THF. As a result, higher efficiency and a shorter analysis time were obtained. When a mixture with 40 mol % CO₂ and 60 mol % THF was used as the mobile phase, the pressure drop across the column decreased by 38% compared with the drop obtained using 100% THF as the mobile phase. Kamlet-Taft solvatochromic parameters p^* and b were used to measure the solvent strength of the THF–CO₂ mixtures. A solvent strength similar to that of pure THF was observed when up to 50 mol % CO₂ was added to THF. No notable deviation in the SEC calibration curve was observed when up to 40 mol % CO₂ was used. However, as a consequence of diminished solvent strength, significant adsorption of solutes to the stationary phase was detected when more than 50 mol % CO₂ was used.

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