Macroscopic-Microscopic Paradox in Dynamic Equilibrium Focusing

Abstract

Recent theoretical and experimental findings concerning equilibrium focusing in density gradient (isopycnic focusing) indicate that the density gradient forming liquid should not necessarily behave as a continuum regarding the focused species. The size of the focused species can be commensurate with the size of the density gradient forming species. Consequently, the microscopic interactions among the gradient forming and focused species must be taken into account while the macroscopic density gradient loses its physical meaning with regard to the mechanism of the focusing. As a result, a paradox appears as concerns the macroscopic and microscopic approaches to explain the focusing phenomenon.