摘要
The paper presents a general retention formula for supercritical fluid chromatography at finite concentration. A new chromatographic rate theory based on the fugacities of solutes instead of concentrations is developed, thus relieving the restrictions of linear isothermal distribution and infinite dilution. An expression for retention values of a N component system including solvent is obtained by combining the rate theory with the mass balance equation of solutes in chromatography. It is shown that there are N-1 characteristic retention peaks for N components and the retention time can be calculated directly from the equilibrium properties of the components in both mobile phase and stationary phase at the given conditions. The theory can be reduced to the well known formula for infinite dilution and to the result of step-pulse theory in gas chromatography under low pressure at finite concentration. Supercritical fluid chromatography may eventually prove itself to be a useful reseach tool in the field of phase equilibrium and thermodynamic properties of supercritical fluid system.
1 INTRODUCTIONSupercritical fluid chromatography(SFC),employing supercritical fluid as mobilephase,originated in the 1960’s [1-4].Since 1980’s extensive research work has beenperformed on SFC,chiefly for analytical purposes [5,6].SFC was then adopted for thedetermination of thermodynamic properties such as partial molar volume,and partialmolar enthalpy of solutes in both mobile phase and stationary phase and the solutedistribution coefficient between two phases [7- 11].Partial molar properties can be de-
