Peptide separations and dissociation constants in nonaqueous capillary electrophoresis: Comparison of methanol and aqueous buffers
- 4 March 2003
- journal article
- research article
- Published by Wiley in Electrophoresis
- Vol. 24 (5), 765-773
- https://doi.org/10.1002/elps.200390096
Abstract
Nonaqueous capillary electrophoresis was evaluated for its potential to separate peptides in methanolic background electrolytes in comparison to aqueous‐methanol (50% v/v) and water. Isomeric aspartyl dipeptides and Leu‐ and Met‐enkephalin served as model compounds. pKa values were determined in the three solvent systems based on the apparent pH scale and in the case of methanol additionally based on the conventional pH scale. Changing from water to methanol led to an increase of the ionization constants describing the dissociation equilibria of the carboxyl group and the amino group, respectively. The pKa shift was more pronounced for the carboxylic acid function leading to a compression of the mobility‐pH curve. As reported for aqueous buffers, efficient separations of the peptides were achieved in methanolic background electrolytes including the resolution of the diastereomers of the isomeric α‐ and β‐aspartyl dipeptides. In contrast to aqueous buffers, the separation of Leu‐ and Met‐enkephalin could also be obtained in buffers in methanol at high pH.Keywords
This publication has 35 references indexed in Scilit:
- Variation of acidity constants of peptides in acetonitrile-water mixtures with solvent composition: effect of preferential solvationChemical Biology & Drug Design, 2009
- Determination of dissociation constant of phosphinate group in phosphinic pseudopeptides by capillary zone electrophoresisJournal of Chromatography B, 2002
- Mobility and ionization constant of basic drugs in methanol. Application of nonaqueous background electrolytes for capillary zone electrophoresis based on a conventional pH scaleJournal of Microcolumn Separations, 2001
- Comparison between capillary electrophoresis, liquid chromatography, potentiometric and spectrophotometric techniques for evaluation of pKa values of zwitterionic drugs in acetonitrile–water mixturesAnalytica Chimica Acta, 2001
- Nonaqueous capillary electrophoresis: A versatile completion of electrophoretic separation techniquesElectrophoresis, 2000
- The application of factor analysis to solvatochromic parameters and pHs values for the standardization of potentiometric sensors in mobile phases used in liquid chromatographyTrAC Trends in Analytical Chemistry, 1999
- Analysis of Tamoxifen and Its Metabolites by On-Line Capillary Electrophoresis−Electrospray Ionization Mass Spectrometry Employing Nonaqueous Media Containing SurfactantsAnalytical Chemistry, 1996
- Microscale Determination of Dissociation Constants of Multivalent Pharmaceuticals by Capillary ElectrophoresisJournal of Pharmaceutical Sciences, 1994
- Isotachophoretic determination of mobility and pKa by means of computer simulationJournal of Chromatography A, 1987
- Effects of solvents and additives on the reaction of N-(benzyloxycarbonyl)-L-aspartic anhydride with L-phenylalanine methyl ester (synthesis of aspartame)The Journal of Organic Chemistry, 1986