Estimation of the dissociation constant for unreacted silanol groups on the surface of ODS-silica from the relationship between ph and electroosmotic flow velocity in capillary electrochromatography

✍ Scribed by Shinya Kitagawa; Takao Tsuda

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 356 KB
• Volume: 7
• Category: Article
• ISSN: 1040-7685
• DOI: 10.1002/mcs.1220070109

✦ Synopsis

Electroosmotic flow in electrochromatography is generated by surface charges on the packing materials under an applied voltage. The surface charge density of ODSsilica gel is increased by dissociation of unreacted silanol groups, and the dissociation constant is dependent on pH. We have developed an equation for the relationship between pH and electroosmotic flow velocity. By using this equation, we estimate the dissociation constant of unreacted silanol groups from their relationships in electrochromatography to be 10-4.3.

The proposed method has the following features: (1) the dissociation constant can be estimated in situ by using a column for electrochromatography or capillary electrophoresis without any alteration of the instrumentation, and therefore (2) the dissociation constant obtained is directly useful for the selection of separation conditions.