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.

Original languageEnglish (US)
Pages (from-to)2693-2698
Number of pages6
JournalAnalytical Chemistry
Issue number15
StatePublished - Aug 1 1996

ASJC Scopus subject areas

  • Analytical Chemistry


Dive into the research topics of 'Dynamic on-column pH monitoring in capillary electrophoresis: Application to volume-limited outlet vials'. Together they form a unique fingerprint.

Cite this