Determination of thermodynamic pKa values of benzimidazole and benzimidazole derivatives by capillary electrophoresis

✍ Scribed by Gilberto Jerez; Gregory Kaufman; Michael Prystai; Sonja Schenkeveld; Kingsley K. Donkor

• Book ID: 102924721
• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: English
• Weight: 577 KB
• Volume: 32
• Category: Article
• ISSN: 1615-9306
• DOI: 10.1002/jssc.200800482

✦ Synopsis

Abstract

Thermodynamic p__K__~a~ values for benzimidazole and several substituted benzimidazoles were determined by CE. Electrophoretic mobilities of benzimidazoles were determined by CE at different pH levels and ionic strengths. The dependence of electrophoretic mobilities on pH was used to obtain p__K__~a~ values at different ionic strengths. Extrapolations to zero ionic strength were used to determine the thermodynamic p__K__~a~ values. Using this method the thermodynamic p__K__~a~ values of 15 benzimidazoles were determined and found to range from 4.48 to 7.38. Results from the CE measurements were compared with spectrophotometric measurements which were evaluated at wavelengths where the highest absorbance difference for varying pH was recorded. The two analytical techniques were in good agreement.