The effect of column verticality on separation efficiency in expanded bed adsorption

The effect of column verticality on liquid dispersion and separation efficiency in expanded bed adsorption columns was investigated using 1 and 5 cm diameter columns. Column misalignment of only 0.15 degree resulted in the reduction of the Bodenstein number from 140 to 50 for the 1 cm dia. column and from 75 to 45 for the 5 cm dia. column. This degree of misalignment was not detectable by visual assessment of adsorbent particle movement within the column. Depending on the relative importance of transport limitations, kinetic limitations and dispersion to any specific separation, this increase in dispersion with column alignment can significantly affect separation efficiency. Pure protein breakthrough profiles resulting from the application of bovine serum albumin onto STREAMLINE Q XL demonstrated that, at 10% breakthrough, 7.8% more protein could be applied to a vertical 1 cm dia. column compared to the same column misaligned by 0.15 degree. When an unclarified yeast homogenate was applied to a 1 cm dia. vertical column packed with STREAMLINE DEAE, 10% breakthrough of glucose-6-phosphate dehydrogenase (G6PDH) corresponded to a load 55% greater compared to the same column aligned 0.185 degree off-vertical. The G6PDH breakthrough curves for vertical and 0.15 degree off-vertical runs performed using a 5 cm column were essentially indistinguishable.