Analytical Sciences

Peak Parking-Moment Analysis Method for the Measurement of Surface Diffusion Coefficients

Kanji MIYABE,* Yuko MATSUMOTO,** and Nobuho ANDO**

*Graduate School of Science and Engineering for Research, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan
**Faculty of Engineering, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan

The peak parking (PP)-moment analysis (MA) method was applied to the measurement of surface diffusion coefficients (D_s) in reversed-phase liquid chromatography using a C₁₈-silica gel and an aqueous solution of methanol (70 vol%). The values of D_s measured by the PP-MA method were in agreement with those obtained by the pulse response (PR)-MA method, which is one of powerful strategies for the quantitative study on the mass transfer kinetics in columns and stationary phases. It was demonstrated that the PP-MA method is an alternative for the experimental measurement of D_s. The mechanism of surface diffusion was considered on the basis of molecular diffusion by introducing a restriction energy (E_r) for surface diffusion. Physical meanings of E_r were discussed by analyzing the correlation between the enthalpy change due to sample retention (Q_st) and D_s. It seems that surface diffusion of a sample molecule is restricted by its retention strength and by the solvent structure formation due to the hydrophobic solvation of the stationary phase surface.

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