Fig. 8 is a schematic of Figs. 5, 5A and 5B, illustrating the use of a carousel, as one embodiment, comprising a series of resin-loaded columns 1, 2, 3 and ranging up to the Nth column, arranged and adapted to provide a serial pathway for the solution 5 from the first column to the Nth column, the interruption in the system at 4 indicating that other resinloaded columns may be present in the syste