Related Experiment Video
Updated: Jul 20, 2026

Capillary Electrophoresis to Monitor Peptide Grafting onto Chitosan Films in Real Time
Published on: October 26, 2016
Propylene carbonate as a nonaqueous solvent for capillary electrophoresis: mobility and ionization constant of
Jan Muzikar1, Tom van de Goor, Bohuslav Gas
1Institute for Analytical Chemistry, University of Vienna, Austria.
Abstract:
The two properties of aliphatic amines were investigated in propylene carbonate as solvent that are decisive for capillary electrophoretic migration: the actual mobilities and the pKa* values. Solutes were eight primary, secondary, and tertiary amines. Roughly, the actual ionic mobilities of the ammonium ions are inversely proportional to the solvent viscosity, fairly obeying Walden's rule. The pKa* values of the cation acids, HB+ (the corresponding acids of the amines, B), were related to the conventional pH* scale of the buffers. Determined from the effective mobilities as a function of the pH*, they are increased by approximately 7 units compared to water. This increase was interpreted based on the concept of the standard free energy of transfer of the individual species in the acid-base equilibrium. The corresponding medium effect on the proton, log mgammaH+ (the logarithm of the transfer activity coefficient mgammaH+) is approximately +8. The medium effect on the free base, B, was obtained from solubility data; it is about -1 and smaller. Plausible values for the medium effect on the cation HB+ (-1 to -2) lead to a sum of the increments, which corresponds with the overall effect, expressed by the change in pKa*. Examination of the individual contributions shows that the drastically lower basicity of propylene carbonate compared to water is mainly responsible for the increase in pKa upon transfer of the acid-base equilibrium of aliphatic ammonium/amine from the aqueous to the organic solvent.
More Related Videos
10:13Using Capillary Electrophoresis to Quantify Organic Acids from Plant Tissue: A Test Case Examining Coffea arabica Seeds
Published on: November 12, 2016
07:54Analysis of AtHIRD11 Intrinsic Disorder and Binding Towards Metal Ions by Capillary Gel Electrophoresis and Affinity Capillary Electrophoresis
Published on: August 22, 2018
Related Concept Videos
Basicity of Aliphatic Amines
To measure the basicity of amines, two conventions are generally used. The first defines Kb as the basicity constant for the deprotonation reaction of water by the amine, as presented in Figure 1. Conventionally, lower Kb indicates higher...
Physical Properties of Amines
Analyte Adsorption and Distribution
Electrophoresis: Overview
There...
Capillary Electrophoresis: Instrumentation
Capillary Electrophoresis: Applications
Capillary zone electrophoresis (CZE) separates ionic components based on their electrophoretic mobility. It has been used to separate proteins, amino acids,...