Continuous radial flow chromatography

Abstract

A prototype of a continuous radial flow chromatograph (CRFC) was developed consisting of a rotating annular bed (14.6 cm O.D., 8.6 cm I.D. and 2 cm deep). A protein-laden feed, equilibration and elution buffer flow radially inwards from a feed chamber at the periphery towards an exit chamber at the axis. Bed movement past fixed feed and exit points allows continuous separation of components from a feed mixture. Continuity equations describing CRFC performance were developed using two resinsolute interaction models. Adsorption was described in both models by the multicomponent Langmuir-Freundlich isotherm (MLF). In the first model (NP) the resin was treated as non-porous and in the second (FD) the resin was porous and mass transfer between flowing solution and resin pores was described by film-diffusion. These models were solved using a finite difference method. Adsorption isotherm and rate parameters were obtained from batch equilibrium, kinetic and axial flow column breakthrough and elution experiments using bovine serum albumin (BSA) and DEAE Sepharose Fast Flow resin. Because MLF caused model instability in breakthrough simulations, the multicomponent Langmuir isotherm (ML) was used. Good agreement was found with axial column breakthrough and elution experiments. NaCl breakthrough was best described by the FD-ML model. Bed dispersion was masked by extra-column dispersion effects. Breakthrough and elution experiments showed that the CRFC had poor resolution when operated in batch mode, due to slow solute distribution in the feed and exit chambers. BSA uptake rates determined by curve fitting were 30 times lower than those found in axial column experiments, indicating poor resolution. FD-ML parameters obtained from continuous extraction of BSA agreed well with data from axial column experiments. CRFC performance can be predicted from small axial column data. The CRFC was used to continuously separate BSA from lactoferrin. 85% of BSA was recovered from the mixture at 94% purity, with a separation factor of 4.8.