Effect of subdividing the adsorbent bed in a five-zone simulated moving bed chromatography for ternary separation

Abstract

A five-zone simulated moving bed (SMB) chromatography, which has been successful in achieving a ternary separation so far, was optimized in this study to separate three nucleoside components (2'-deoxycytidine, 2'-deoxyguanosine, and 2'-deoxyadenosine) with high purity. For such an optimized process, we investigated how the subdivision of its chromatographic bed affects the wave dynamics and separation performance, which has been one of the important issues in the area of a continuous chromatographic separation process design. It was found that the migration or propagation behavior of the highest affinity component (2'-deoxyadenosine) virtually controlled the wave dynamics and separation performance of the five-zone SMB chromatography. Unlike the lowest affinity and the intermediate affinity components (2'-deoxycytidine and 2'-deoxyguanosine), the highest affinity component generated more than two solute bands, which were scattered in several zones. As the degree of bed subdivision became higher, the scattered solute bands of the highest affinity component were gradually merged, leading to a seemingly single solute band with a wavy plateau. Eventually, the wavy plateau became flat. Such behavior of the highest affinity component brought about a visible change in its average concentrations at the two product ports, and a significant reduction in the purity of the intermediate affinity component. The results of this study can serve as a useful summary of five-zone SMB behaviors, and as the first step for the development of new strategies on five-zone SMB performance.