Abstract
Adsorptive separations by high performance liquid chromatography (HPLC) are important processes in biotechnology for the separation of proteins. Packing materials for chromatographic separations of proteins have been continuously improved in order to reduce intraparticle mass transfer resistances. The objective of this paper is to understand and characterise mass transfer mechanisms inside POROS HQ/M particles (PerSeptive Biosystems, Framingham, MA, USA) combining theory with experimental work. Elution chromatography under non-retained conditions and frontal chromatography in retained conditions of two proteins, myoglobin and bovine serum albumin (BSA), were studied. Elution chromatography experiments show that the mass transfer resistance in POROS HQ/M is substantially reduced by intraparticle convection. Adsorption equilibrium isotherms were measured from experimental breakthrough curves. The adsorption of myoglobin (with 0.1 M NaCl) follows a linear isotherm, whereas the adsorption of BSA (with no NaCl or with 0.1 M NaCl) follows Langmuir isotherms almost rectangular in shape. Three mathematical models, accounting for adsorption on throughpore walls and inside microparticles of POROS particles and intraparticle convection in throughpores, were developed in this study and used in the modelling of experimental breakthrough curves of myoglobin and BSA. Experimental convection effects in POROS HQ/M particles are higher than those predicted by these models and the extra effects can be attributed to a flow rate dependent film resistance around microparticles.
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