Dynamic On-Column pH Monitoring in Capillary Electrophoresis: Application to Volume-Limited Outlet Vials
- 1 August 1996
- journal article
- Published by American Chemical Society (ACS) in Analytical Chemistry
- Vol. 68 (15) , 2693-2698
- https://doi.org/10.1021/ac960166b
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.Keywords
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