Alternative method to study the radial dispersion in liquid chromatography columns. Part II: Experimental

The present contribution reports on the practical implementation and validation of a new experimental method to determine the radial dispersion (D_rad) in packed bed liquid chromatography columns, as well as on the results obtained with it. A first important validation was that the measured D_rad-values were independent of the applied relative central flow rate (varied from 25% to 57%). The obtained D_rad-values did not vary significantly when changing the concentration of the injected tracer to check potential mass overloading effects (25, 50 or 75 ppm of tracer for the acetophenone measurements; 12.5 and 25 ppm of tracer for the toluene measurements). And yet another important validation step was the observation that the D_rad-values clearly converged to the value of D_eff for velocities going to zero, as physically and theoretically expected. Plotting the obtained results as a plot of D_rad/D_mol versus the reduced velocity ν, a quasi-linear relationship is obtained. The slope of the curve (β = 0.38 and β = 0.46 for toluene and acetophenone, respectively) is significantly larger than the value that is most frequently cited in engineering literature. However, the obtained β-values and D_rad/D_mol-values still fall within the broad range of β- and D_rad/D_mol-values cited in literature.