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Updated: Jul 10, 2026

On-chip Isotachophoresis for Separation of Ions and Purification of Nucleic Acids
Published on: March 2, 2012
Do zwitterions contribute to the ionic strength of a solution?
Earle Stellwagen1, Jason D Prantner, Nancy C Stellwagen
1Department of Biochemistry, University of Iowa, Iowa City, IA 52242, USA.
Abstract:
Capillary electrophoresis has been used to determine whether zwitterions contribute to the ionic strength of a solution, by measuring the mobility of a double-stranded DNA oligomer in cacodylate-buffered solutions containing various concentrations of the ionic salt tetraethylammonium chloride (TEA(+)Cl(-)) or the zwitterion tricine(+/-). The mobility of the DNA decreased as the square root of ionic strength, as expected from the Debye-Hückel-Onsager theory of electrophoresis, when TEA(+)Cl(-) was added to the buffer. However, the mobility was independent of the concentration of added tricine(+/-). Hence, zwitterions do not contribute to the ionic strength of a solution.
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