Suppression of electroosmotic flow and prevention of wall adsorption in capillary zone electrophoresis using zwitterionic surfactants

Addition of zwitterionic surfactants such as dodecyldimethyl(3-sulfopropyl)ammonium hydroxide, hexadecyldimethyl(3-sulfopropyl)ammonium hydroxide, and coco (amidopropyl)hydroxyldimethylsulfobetaine (Rewoteric AM CAS U) to an electrophoretic buffer suppress the electroosmotic flow by 50-90%. Onset of suppression occurs at approximately the critical micelle concentration of the surfactant. CAS U effectively suppresses the electroosmotic now over the pH range 3-12. Addition of 2 mM CAS U to the electrophoretic buffer prevents adsorption of cationic proteins lysozyme, alpha-chymotrypsinogen A, cytochrome c, and ribonuclease A. Migration time reproducibility for these proteins is similar to 1% RSD within 1 day and 2-5% from day to day. Efficiencies in excess of 750000 plates/m and recoveries of >80% were observed for protein injections from distilled water. Alternatively if 2 mM CAS U is added to samples, recoveries were quantitative, although efficiencies decreased to 325000-600000 plates/m. The natural electroosmotic now of the capillaries is regenerated simply by rinsing with sodium hydroxide.