Diffusive-convective and diffusive-electroconvective transport in non-uniform channels with application to macromolecular separations

The effects of various geometrical parameters on effective diffusive, conve ctive and electroconvective transport coefficients are studied by using mod els of constricted and expanded pores. The analysis of these simple pores o ffers insight into the transport behavior of macromolecules in media consis ting of anisotropic aligned pores. A number of cases are analyzed including hydrodynamic flow, hindered transport with hydrodynamic flow, and electrop horetic transport with and without hindrance. The effects of the geometrica l parameters of the model pores on the effective transport parameters are d etermined. The implications of changes of these geometrical parameters, app lied electrical fields, and bulk flow rates on separations are illustrated using the time required to separate a binary mixture of solutes for specifi ed resolutions. The results show that by appropriately selecting the flow r ate in the case of hydrodynamic flow or the electrical field strength for t he case of electrophoresis an optimum or minimum time of separation can be determined for the separation of two comparably sized molecules with sizes close to those of the narrower part of the pore. (C) 1999 Elsevier Science B.V.