Correlation of resolution with frictional coefficients and pKa values in capillary electrophoresis of four diuretics: Determination of electric field strength and electroosmotic velocity
✍ Scribed by Juho H. Jumppanen; Heli Sirén; Marja-Liisa Riekkola; Olle Söderman
- Publisher
- John Wiley and Sons
- Year
- 1993
- Tongue
- English
- Weight
- 483 KB
- Volume
- 5
- Category
- Article
- ISSN
- 1040-7685
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✦ Synopsis
Abstract
Under ideal conditions in capillary zone electrophoresis, the frictional coefficients (f) and pK~a~ values of the analytes can be used to predict their separation under various conditions. These parameters can also be used to determine whether or not the separation depends solely on electrophoretic mobilities. Moreover, marker compounds with known electrophoretic mobilities can be used in ideal systems to yield information on pK~a~ values or on frictional coefficients for molecules at infinite dilution that cannot be studied by more widely used techniques. Fourier transform pulse gradient spin‐echo nuclear magnetic resonance spectroscopy is a standard method for measuring diffusion coefficients, from which the frictional coefficients were obtained. The good correlation between measured values of f and the observed elution times of four diuretics at pH 10.6 (20°C, CAPS 0.06 M) proved that the separation was based on the electrophoretic mobilities only. To be able to study the system accurately, the field strength and electroosmotic flow were measured empirically by using acetazolamide and clopamide as markers. The electric field strength in the electrolyte was found to be approximately 20% lower than expected. Simple equations are presented, which allow the measurement of these two quantities with the help of two compounds of known electrophoretic mobilities. To yield reliable results, the compounds should have electrophoretic mobilities differing by a factor of 2 or more.