Suppression of Electroosmotic Flow and Prevention of Wall Adsorption in Capillary Zone Electrophoresis Using Zwitterionic Surfactants

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Abstract
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 flow over the pH range 3−12. Addition of 2 mM CAS U to the electrophoretic buffer prevents adsorption of cationic proteins lysozyme, α-chymotrypsinogen A, cytochrome c, and ribonuclease A. Migration time reproducibility for these proteins is ∼1% RSD within 1 day and 2−5% from day to day. Efficiencies in excess of 750 000 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 325 000−600 000 plates/m. The natural electroosmotic flow of the capillaries is regenerated simply by rinsing with sodium hydroxide.