Chromatography Optimization Strategy - Robust packing procedures can improve process performance and increase resin lifetime. - BioPharm International

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Chromatography Optimization Strategy
Robust packing procedures can improve process performance and increase resin lifetime.


BioPharm International
Volume 22, Issue 3


Figure 3. Volumetric versus mass ratio
Therefore, a relationship between volumetric and mass ratio was established to optimize the advantages of methods described earlier. The relationship was generated through a plot of volumetric ratio (GS and FC) versus mass retained (Figure 3). The data showed a region of linear relationship between volumetric and mass retained ratios. Given that the GS method was historically unstable, the centrifuge method was related to the FC method. A plot of mass retained versus volumetric ratios demonstrate a linear relationship within the tested range.

Using the centrifuge method for resin determination significantly reduced the packing procedure cycle time from greater than 70 hours down to 60 minutes. This method was important in the process characterization strategy because it paved the way to rapidly complete numerous packs at bench and large scales and thereby reduced the characterization timeframe and raw material consumption.

COMPRESSIBLE MEDIA PRESSURE-FLOW CHARACTERISTICS

A small-scale study was established to understand the hydrodynamic properties to forecast effects of resin amount before consuming expensive raw materials and efforts at large-scale. This provided the advantage to predict the column performance at given conditions of resin amount, fluid properties, and flow rates at various aspect ratios. Pressure-flow studies were executed at small scale. The model was tested with resin slurry at applicable process temperatures. The experimental plan was based on the work performed by Jonathan Stickel and Alexandros Fotopoulos.3 Pressure and bed height for various aspect ratios were collected on flow-rate increments until a maximum flow rate was achieved. Bench-scale experiments on a 100-mm diameter column reached maximum compressions of approximately 20.4% average at various aspect ratios.

The results from small-scale experiments provided a linear expression on the plot of the critical velocity (u CRI) versus aspect ratio with slope and intercept values of 349.97 cm2/h and 3718.88 cm2/h respectively (Equation 4):





Figure 4. Critical velocity versus aspect ratio
in which u CRI is the critical flow velocity as a function of AR given in cm/h, L0 is the gravity settled bed height given in cm, and D is the column inner diameter given in cm. This expression is capable to predict maximum flow rates as a function of column aspect ratio, which is dictated by the desired compression on a column (Figure 4).

The relation of aspect ratio and flow rate was embedded into the Blake-Kozeny equation below (Equation 5) to predict pressure drop as a function of flow rate.





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