Peak Parking - Moment Analysis. A Strategy for the Study of the Mass-Transfer Kinetics in the Stationary Phase

摘要

The combination of peak parking and moment analysisis proved to be a powerful strategy for studying the molecular diffusivity of solute molecules in stationary phases and for determining the corresponding kinetic parameters. The physical meaning of the traditional kinetic parameter, (gamma)_(s)D_(s), the diffusion coefficient of solute molecules in stationary phases, is first clarified. A second kinetic parameter, D_(Ls), is then derived from (gamma)_(s)D_(s), and the correspondence between D_(Ls) and the surface diffusion coefficient, D_(sur), is discussed. Then, the results of peak parking experiments carried out with RPLC systems using aqueous methanol solutions and C_(18)-silica columns are reported. The moments of pulse responses were measured and are analyzed. The values and some characteristics of D_(Ls) measured by the peak parking-moment analysis method are compared with those of D_(sur) determined using the pulse response-moment analysis method. The comparison of the numerical values of D_(Ls) and D_(sur) suggests that D_(Ls) is nearly equal to D_(sur) and that it exhibits the same dependence on the retention strength as does D_(sur) with regard to the mass-transfer kinetics and extrath-ermodynamics. This comparison allows us to conclude that D_(Ls) corresponds to D_(sur). The advantages and disad-vantages of the peak parking-moment analysis method were compared with those of the pulse response-moment analysis method. The combination of these two methods provides a comprehensive strategy for measuring the mass-transfer kinetics in the stationary phase.