Page 201 - Chiral Separation Techniques

6.9 Other Separation Formats 179

vance for bioanalytical applications was the functionalization of the outer surface of
a polymer imprinted with (S)-naproxen with a hydrophilic polymer layer (Fig. 6-15).
This led to a slight decrease in the separation efficiency, but allowed on the other
hand direct injection of plasma samples on the columns.

Fig. 6-15. Synthetic scheme of surface-modified MIP for (S)-naproxen. V65 = 2,2’-azobis(2,4-
dimethylvaleronitrile); GMMA = glycerolmonomethacrylate; GDMA = glyceroldimethacrylate.

6.9 Other Separation Formats

As mentioned in the introduction, due to the high enantioselectivities exhibited by
the imprinted chiral phases, applications in batch-, SMB-, bubble- or membrane-
based separation processes may become attractive. The concept of applying MICSPs
for bubble fractionation of enantiomers was demonstrated recently [99]. This sepa-
ration principle can be useful for separations of large amounts of material at very low
costs, and is an important technique for concentrating sulfide ores. For this process
to be practical a high enrichment factor is needed and the chiral collector should be
easy to recycle. This is the case of solid collectors such as imprinted polymers which
also have the benefit of high robustness. Thus L-PA-imprinted polymer particles of
less than 20 µm adhered to air bubbles and were effectively transported to the top of
the bubble column (Fig. 6-16). The particles were first pre-equilibrated with a solu-
tion of the racemate, and then added to the separator. Here, they separated after bub-
ble flotation to the top of the column. Enantiomerically enriched compound was then
obtained by washing of the particles that in turn could be recycled. By using fine