Analysis on mass-transfer phenomena in reversed-phase liquid chromatography.

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  • 逆相液体クロマトグラフィーにおける物質移動現象の解析
  • ギャクソウ エキタイ クロマトグラフィー ニ オケル ブッシツ イドウ ゲンシ

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Abstract

An analytical study was made concerning mass-transfer phenomena in reversed-phase liquid chromatography (RP-LC). A moment method was applied for analyzing the properties of chromatographic peaks measured under various conditions related to sample substances as well as stationary and mobile phases. First moment analyses provided some pieces of information concerning the mass-transfer equilibrium in RP-LC. The isosteric heat of adsorption (-Qst) was smaller than the corresponding heat of vaporization. The relatively small value of-Qst could be explained by solvophobic theory. From second moment analyses, it was indicated that the contribution of intraparticle diffusion to the overall mass-transfer resistance in a column was usually important, and that surface diffusion played a significantly dominant role for mass transfer in RP packing materials. The activation energy of the surface diffusion (Es) was larger than -Qst in RP-LC. The correlation between Es and Qst could be quantitatively interpreted based on the absolute rate theory by assuming that surface diffusion was an activated process similar to molecular diffusion in the liquid phase. The establishment of both an enthalpy-entropy compensation effect and a linear free-energy relation was confirmed irrespective of the separation conditions in RP-LC. A nondimensional rate equation was derived on the basis of moment analysis theory. The equation consists of several terms representing the contributions of mass-transfer processes, such as molecular diffusion, eddy diffusion, fluid-to-particle mass transfer, and intraparticle pore and surface diffusions, to peak spreading. The influence of some operational parameters on the column efficiency was numerically analyzed while considering the individual contribution of each term. It was demonstrated that fundamental studies of surface diffusion provided some essential pieces of information for elucidating the separation mechanism in RP-LC.

Journal

  • BUNSEKI KAGAKU

    BUNSEKI KAGAKU 47 (11), 769-782, 1998

    The Japan Society for Analytical Chemistry

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