Chitosan coated capillary with reversed electroosmotic flow in capillary electrophoresis for the separation of basic drugs and proteins

An enhanced surface coating method was developed for capillary electrophoresis (CE) using the natural polymer chitosan. The cationic property of chitosan at pH below 6.5 created a reversed electroosmotic flow (EOF) in the capillary. The EOF changed significantly with the run buffer pH at values below 4.0, with less pH dependency at values in the pH range of 4.0‐5.5. The new coating exhibited good performance reproducibility. The relative standard deviation (RSD) of EOF was 0.77%. The EOF changed an average of 2.4% after 10 h normal use. The EOF started to change significantly after a constant electric field (300 v cm −1 ) had been applied for 20 h. This capillary with a reversed EOF can be used to reduce the solute‐wall interaction problem for separations of basic analytes, for example, separations of positively charged proteins and basic drug enantiomers.