Chromatographic Analysis of Limonene and Linalool on Silica Gel in Supercritical Carbon Dioxide

ABSTRACT

Adsorption behavior of limonene and linalool, which are respectively the principal constituents of terpene and oxygenated compounds in citrus oil, on silica gel in the presence of supercritical carbon dioxide was analyzed by the tracer response method. In this study a two-column system was used to eliminate the effect of nonideal behavior at the sample injection. Adsorption equilibria and mass transport properties were evaluated by means of the moment method at pressures of 8.8–23.5 MPa and temperatures of 313–333 K. The adsorption equilibrium constant was larger for higher temperature and lower pressure when linalool was selectively adsorbed on silica gel. The apparent heat of adsorption ranged from –20 to 230 kj/mol. The Peclet number and the ratio of intraparticle effective diffusivity to molecular diffusivity were 0.013–0.257 and 0.002–0.716, respectively.

Key Words::

• Supercritical fluid
• Moment method
• Adsorption equilibrium constant
• Mass transfer
• Citrus oil