Characterization of electrical charge separation at the interface of two aqueous solutions in the presence of concentration gradients and cation/anion mobility ratio asymmetry
Physical consequences of ionic diffusion processes play a major role on the outcome of electrophysiology experiments due to both their contribution to the ionic transmembrane transport and phenomena taking place at the measuring instruments interface. As most of the time heterogenities in biological media with respect to ionic diffusion constants are disregarded, we intended to look upon the general case of ionic diffusion at the interface of two liquids on which gradients of these diffusion constants no longer can be neglected. We developed a theoretical model for the diffusion potential which emerges at an aqueous interface under gradients of concentration and diffusion constants. The experimental validation of our model was achieved through potential difference measurements of the diffusion potential between two solutions containing sodium chloride (NaCl) and glycerine solutions of various concentrations. Within the studied domain of the electrical charge mobility ratio, we noticed that experimental results are in agreement with the theoretically inferred diffusion potential values. This demonstrates that the resulting relationship for the diffusion potential inferred from our model could be applied for other cases, as well. When the ionic solutions contains an indefinite quantity of glycerine or an unknown substance able to modify diffusion constants of sodium and chloride, it was shown that through measurements of the diffusion potential one can infer the unknown concentration of glycerine and the modified ionic mobility ratio. This, in turn, builds up the foundation for a novel yet simple and efficient analitycal sensing device for quantitative determination in the field.
- Faculty of Physics of Department of Medical Physics & Biophysics, Alexandru I. Cuza University, Blvd, Carol I no. 11, Iasi, Romania
- Faculty of Physics of Department of Medical Physics & Biophysics, Alexandru I. Cuza University, Blvd, Carol I no. 11, Iasi, Romania, email@example.com
-  O.S. Knudsen:Biological membranes, Cambridge University Press, 2002.
-  G. Moy, B. Corry, S. Kuyucak and C. Chin-Ho: “Tests of Continuum Theories as Models of Ion Channels. I. Poisson-Boltzmann Theory versus Brownian Dynamics,”Biophysical Journal,Vol. 78, (2000),pp. 2349–2363.
-  D. Chen and R. Eisenberg: “Charges, currents, and potentials in ionic channels of one conformation”,Biophysical Journal,Vol. 64, (1993),pp. 1405–1421. http://dx.doi.org/10.1016/S0006-3495(93)81507-8[Crossref]
-  N.M. Kocherginsky and D. Rajarathna: “Measurements of Transmembrane Potential and Ionic Selectivity of Biomimetic Membranes”, In:Proceedings of the 2003 WFEO/ASEE e-Conference, American Society for Engineering Education, 2003.
-  S. Mafe, P. Ramirez, A. Tanioka and J. Pellicer: “Model for Counterion-Membrane-Fixed Ion Pairing and Donnan Equilibrium in Charged Membranes”,Journal of Chemical Physics, Vol. 101, (1997), pp. 1851–1856.
-  G.D. Mehta, T.F. Morse, E.A. Mason and L. Daneshpajooh: “Generalized Nernst-Planck and Stefan-Maxwell equations for membrane transport”,Journal of Chemical Physics,Vol. 64, (1976),pp. 3917–3923. http://dx.doi.org/10.1063/1.432021[Crossref]
-  Z. Schuss and B. Nadler: “Derivation of Poisson and Nernst-Planck equations in a bath and channel from a molecular model”,Physical Review E, Vol. 64, (2001), pp. 1–14. http://dx.doi.org/10.1103/PhysRevE.64.036116[Crossref]
-  D.T. Gillespie: “The chemical Langevin equation”,Journal of Chemical Physics,Vol. 113, (2000),pp. 297–306. http://dx.doi.org/10.1063/1.481811[Crossref]