Fast and easy coating for capillary electrophoresis based on a physically adsorbed cationic copolymer

In this work, a new copolymer synthesized in our laboratory is used as physically adsorbed coating for capillary electrophoresis (CE). The copolymer is composed of ethylpyrrolidine methacrylate (EPyM) and methylmethacrylate (MMA). The capillary coating is easily obtained by simply flushing into the tubing an EPyM/MMA solution. It is demonstrated that the composition of the EPyM/MMA copolymer together with the selection of the background electrolyte (BGE) and pH allow tailoring the direction and magnitude of the electroosmotic flow (EOF) in CE. It is also shown that the EOF obtained for the EPyM/MMA-coated capillaries was reproducible in all cases independently on pH or polymer composition. Thus, RSD values lower than 1.9% (n = 5) for the same capillary and day were obtained for the migration time, while the repeatability interdays (n = 5) was observed to provide RSD values lower than 0.5%. The stability of the coating procedure was also tested between capillaries (n = 3) obtaining RSD values lower than 0.6%. It is demonstrated with several examples that the use of EPyM/MMA coatings in CE can drastically reduce the analysis time and/or to improve the resolution of the separations. It is shown that EPyM/MMA-coated capillaries allow the separation of basic proteins by reducing their adsorption onto the capillary wall. Also, EPyM/MMA-coated capillaries provide a faster separation of samples containing simultaneously positive and negative analytes. Moreover, it is demonstrated that the use of EPyM/MMA-coated capillaries can incorporate an additional chromatographic-like interaction with nucleosides that highly improves the separation of this group of solutes.