Is it true that ionic interaction is slower than hydrophobic Van der Waals absorption / desorption interactions?
That is probably not true. At least the difference is not significant in the chromatography time scale. The main limitation is usually diffusion from and in the pores. It is why smaller particle packing always gives higher efficiency per meter than bigger particle columns. They simply have shorter pores. Ionic interaction is generally very strong but it is reduced significantly by the ion-exchange process (competing ions from the mobile phase), so the rate should be close to the diffusion rate. Otherwise, no good chromatography is possible. back to top You have achieved an almost Gaussian peak-shape with your phases, even though your phases are not much different from very old RP columns with a lot of ionizable silanol groups exposed. Primesep phases have many more ionizable groups for ionic interaction than an RP column has residual silanol groups, especially at an acidic pH. In addition, silica gel has more than one type of silanol group (three types well characterized) with probably
