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Electrophoretic Separation of Proteins
Published on: June 12, 2008
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The electrophoretic mobility of an uncharged particle
Richard W O'Brien1, James K Beattie1, Alex M Djerdjev1
1School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia.
Journal of Colloid and Interface Science
|February 25, 2014
Summary
Electrophoretic mobility in uncharged particles is transient, not steady. Double-layer polarization quickly halts motion, indicating negative mobility implies negative charge for hydrophobic particles.
Area of Science:
- Colloid and surface science
- Physical chemistry
- Electrokinetics
Background:
- Electrophoretic mobility is a key parameter in characterizing particle surface charge.
- It is conventionally assumed that negative electrophoretic mobility indicates a negatively charged particle.
- However, some studies suggest uncharged particles can exhibit negative mobility.
Purpose of the Study:
- To investigate the electrophoretic behavior of uncharged particles.
- To determine if steady-state electrophoresis is possible for uncharged finite particles.
- To reconcile experimental observations with theoretical predictions.
Main Methods:
- Theoretical analysis of double-layer polarization around particles.
- Molecular Dynamics simulations of infinite slabs.
- Comparison with experimental data for oil drops in aqueous solutions.
Main Results:
- Steady-state electrophoresis is not possible for uncharged finite particles due to charge buildup.
- Initial motion of uncharged particles ceases rapidly due to double-layer polarization.
- Experimental data shows mobility decreases with increasing salt concentration, consistent with negative particle charge.
Conclusions:
- Transient electrophoretic motion of uncharged particles is quickly quenched.
- Negative electrophoretic mobility in hydrophobic particles is reliably indicative of a negative surface charge.
- The compression of the electrical double layer with increasing salt concentration explains the observed experimental trends.
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