INVESTIGATIONS IN HPLC SYSTEM CONTAINING SILICA DYNAMICALLY MODIFIED BY CAMPHORSULFONIC ACID

The adsorption of camphorsulfonic acid (CSA) by silica was followed by the break-through method using methanol-water-CSA and acetonitrile-water-CSA mixture as mobile phases. The break-through curves comprise two distinct waves, indicating the formation of CSA-double layer on the silica surface. The amount of CSA bound in the 1. and 2. layer is a function of the methanol-, acetonitrile- and CSA-content of the eluent. Following the retention of a model substance along the break-through curve from methanol-water-CSA eluent, the different sorptional feature of the two CSA layers was revealed: retention increase followed by the depression of the retention could be observed before and after the first break-through point respectively. Further study of these appearances is in progress.