Batch chromatography with recycle lag. I-Concept and design

This is the first of a two-part study in which we explore the concept of batch chromatography with recycle lag, concluding with the design, construction, and experimental validation of a prototype that embodies the physical realization of this concept. Moreover, the apparatus is simple to set up in particular in view of large-scale applications. Here the theory behind batch chromatography with recycle lag is revisited and extended, with emphasis on the mathematical formulation and procedure for deriving the single-column batch analogue of any variant of multicolumn simulated countercurrent chromatography. By resorting to selected examples, namely GE Healthcare Bio-science's three-column periodic countercurrent chromatography, Novasep's sequential multicolumn chromatography, and a few hypothetical multicolumn processes, we discuss how the theory can be operationalized. Finally, we conclude by describing the design of a device or apparatus-an eluate recycling device (ERD)-to physically realize the proposed concept. The ERD implements an approximate "first in, first out" method for organizing and manipulating the to-be-recycled fractions of eluate collected from the chromatography column, where the oldest (first) amount fluid, or 'head' of the fraction, is the first to exit and be recycled to the column.