Calibration-free concentration determination of charged colloidal nanoparticles and determination of effective charges by capillary isotachophoresis |
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Authors: | Ute Pyell Wendelin Bücking Carolin Huhn Barbara Herrmann Alexey Merkoulov Joachim Mannhardt Hartmut Jungclas Thomas Nann |
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Institution: | (1) Department of Chemistry, University of Marburg, Hans-Meerwein-Strasse, 35032 Marburg, Germany;(2) Freiburg Materials Research Centre (FMF), Albert-Ludwig University of Freiburg, Stefan-Meier-Strasse 21, 79104 Freiburg, Germany;(3) J&M Analytik AG, Willy-Messerschmitt-Strasse 8, 73457 Essingen, Germany;(4) School of Chemical Sciences and Pharmacy, University of East Anglia (UEA), Norwich, NR4 7TJ, UK |
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Abstract: | Although colloidal nanoparticles show an electrophoretic heterogeneity under the conditions of capillary electrophoresis,
which can be either due to the particle-size distribution and/or the particle shape distribution and/or the zeta-potential
distribution, they can form correct isotachophoretic zones with sharp-moving boundaries. Therefore, the technique of isotachophoresis
permits to generate plugs in which the co-ions and counter ions of the original colloidal solution are removed and replaced
by the buffering counter ions of the leading electrolyte. It is shown that analytical isotachophoresis can be used to measure
directly, without calibration, the molar (particle) concentration of dispersed ionic colloids provided that the transference
number and the mean effective charge number of the particles (within the isotachophoretic zone) can be determined with adequate
accuracy. The method can also be used to measure directly the effective charge number of biomacromolecules or colloidal particles,
if solutions with known molar (particle) concentration can be prepared. The validity of the approach was confirmed for a model
solution containing a known molar concentration of bovine serum albumin.
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