title: Dynamic on-column pH monitoring in capillary electrophoresis: application to volume-limited outlet vials.
abstract: With capillary electrophoresis, buffer pH must be constant to achieve consistent migration times. Irreproducible separations have been attributed to pH changes due to water hydrolysis in the inlet/outlet vials. A method of measuring the pH of the electrolyte on-column is described that uses wavelength-resolved fluorescence detection. C.SNARF-1 is a fluorescent pH indicator that has a large change in fluorescence emission profile depending on pH. When it is incorporated into the running buffer, monitoring the pH-dependent emission spectra of the C.SNARF-1 allows column pH to be calculated. With reduced-volume outlet buffer vials in the nanoliter to low microliter range, significant changes in pH and column conductivity are measured during a single electrophoretic run, with pH fronts greater than 3 units passing a fixed point on the capillary over a several second period. These changes appear to be caused by reverse-migrating OH- produced at the capillary outlet by the hydrolysis of water.
authors.affiliation: Department of Chemistry, University of Illinois, Urbana 61801, USA.
authors.forename: A
authors.initials: A
authors.lastname: Timperman
authors.forename: S E
authors.initials: SE
authors.lastname: Tracht
authors.forename: J V
authors.initials: JV
authors.lastname: Sweedler
mesh_terms: D019075:Electrophoresis, Capillary; D006863:Hydrogen-Ion Concentration