Batch chromatography with recycle lag. II-Physical realization and experimental validation

This is the second 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-an eluate recycling device (ERD)-that embodies the physical realization of this concept. The ERD implements an approximate "first in, first out" method of 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 back to the column. Moreover, the apparatus is simple to set up in particular in view of large-scale applications. Here we detail the construction of the ERD and assembly of a setup to interconnect the ERD and a chromatography column. Through the coordinated operation of two-way valves and two-position six-port switching valves it is possible to implement a diverse set of configurations or operating modes interconnecting the chromatography column and the ERD. The setup is validated experimentally with success using the separation of a nucleoside mixture by reversed phase chromatography as a model problem. It is also shown that by redesigning the fluid distributor using 3D printing technology the ERD performance can be improved.