Moving chemical reaction boundary and isoelectric focusing - I. Conditional equations for Svensson-Tiselius' differential equation of solute concentration distribution in idealized isoelectric focusing at steady state

In this paper, the differential equation, which is formulated by Svensson-Tiselius for the concentration distribution of protolytes in idealized isoelectric focusing (IEF) at steady state, is discussed. The general condition equations are formulated for Svensson-Tiselius' differential equation, and from the general conditional equations, the conditional equations for the acidic anolyte and alkaline catholyte used in Svensson's IEF are derived. It is theoretically shown that the condition equations for the anolyte and catholyte are the same as the stationary neutralization reaction boundary equations (SNRBEs) that can be deduced from the moving chemical reaction boundary equations (MCRBEs) in special cases. The conditional equations for the anolyte and catholyte reveal that an idealized IEF, viz., a stable pH gradient in IEF, can be achieved, if the fluxes of protons and hydroxyl ions migrating in opposite directions are equal to each other. According to the conditional equations for the anolyte and catholyte and the fact that the pH gradient in Svensson's IEF is quasi-stable, but not completely stable (due to the drifts and plateau of the pH gradient in IEF), one can infer that the quasi/equal fluxes of hydrogen and hydroxyl ions must be present in Svensson's IEF. As shown in the accompanying paper, this inference coincides with important findings, i.e. the existence of quasi/equal fluxes of hydrogen and hydroxyl ions in stationary electrolysis, on which Svensson's IEF is based. (C) 1998 Elsevier Science B.V. All rights reserved.