Resin coating for capillaries giving a net positive charge and great potential for customised modification of surface properties

The use of capillary coatings in capillary electrophoresis to manipulate electroosmotic flow (EOF) and chemical interactions is an expanding field,which has generated much interest. In this study the use of a reactive polyamide resin is explored, which is straightforwardly applied to give a positively charged coating on the capillary wall. A permanent positive coating offers distinct advantages, particularly in the analysis of low-molecular-mass anions. Analysis of such highly mobile anions has usually been achieved by the addition of cationic surfactant (EOF modifier) to the electrolyte, to provide a temporary positive coating on the wall, reversing the direction of EOF within the capillary and, under appropriate conditions, forcing the anions towards the detector. The more permanent positive charge achieved here eliminates the need for such electrolyte additives. Additionally, the coating chemistry is such that there is potential for further modification to provide great flexibility in manipulation of surface properties. This offers the possibility of various coatings to suit a wide range of applications.