Computational fluid dynamics study of potential solutions to alleviate viscous heating band broadening in 2.1 millimeter liquid chromatography columns

Flow behavior of protein solutions in a lab-scale chromatographic system

A fluid dynamics model has been developed to describe flow behavior in a lab-scale chromatographic system dedicated for protein processing. The case study included a detailed analysis of elution pattern of a protein, which was a monoclonal antibody, glycerol, and their mixtures in aqueous solutions. Glycerol solutions mimicked viscous environment of the concentrated protein solutions. The model accounted for concentration dependences of solution viscosity and density, and dispersion anisotropy in the packed bed. It was implemented into a commercial computational fluid dynamics software using user-defined functions. The prediction efficiency was successfully verified by comparing the model simulations in the form of the concentration profiles and their variances with the corresponding experimental data. The contribution of the individual elements of the chromatographic system to protein band broadening was evaluated for different configurations: for the extra-column volumes in the absence of the chromatographic column, for the zero-length column without the packed bed and for the column containing the packed bed. The influence of the operating variables, including: the mobile phase flowrate, the type of the injection system, i.e., the injection loop capillary or the superloop, the injection volume and the length of the packed bed, on band broadening of the protein was determined under nonadsorbing conditions. For protein solutions having viscosity comparable with the mobile phase, the flow behavior either in the column hardware or in the injection system made major contributions to band broadening, which depended on the type of the injection system. For highly viscous protein solution, the flow behavior in the packed bed exerted a dominant influence on band broadening.

Detailed computational fluid dynamics study of the parameters contributing to the viscous heating band broadening in liquid chromatography at pressures up to 2500 bar in 2.1 mm columns

Over the past years viscous heating band broadening occurring in high pressure liquid chromatography has been studied extensively. In the present numerical study, we investigate the fine details of this band broadening contribution under extreme high-pressure conditions (2500 bar). To analyze the results, we first show that viscous heating leads to two clearly distinguishable band broadening effects, one originating from the radial differences in the species migration velocity and the other from the axial variations. It was found that the radial contribution is independent of the intrinsic band broadening of the bed (i.e. band broadening in absence of viscous heating) while it strongly depends on the radial dispersion coefficient and the retention enthalpy of the analytes. On the other hand, the axial contribution is strongly dependent on the bed intrinsic band broadening and it is found to be 4 to 5 times lower than the radial contribution. We also show the strong effect of the endfittings on the temperature gradients inside the column thus on the resulting viscous heating band broadening.