The separation behaviors of four different groups of pharmaceuticals were i
nvestigated using cholesteryl-10-undecenoate and ODS phases. The cholestery
l phase, which has liquid crystal properties, showed different selectivity
and retention behavior from those of ODS phase. The difference is on its ap
parent ability to recognize specific structures in the molecules, discrimin
ate among derivatives, or subsequently recognize modifications done on thes
e structures. However, on ODS phase the hydrophobicity effects seem to take
precedent as the main factor in its retention mechanism. This enhanced sel
ectivity of the cholesteryl phase is attributed to three contributing struc
tures found in its structure; the long hydrocarbon chain that gives added m
obility to the phase, the carbonyl group which can interact with a variety
of substituent groups, and the cholesteric moiety which can invoke pi-pi in
teraction as well as steric effects. The use of the cholesteryl phase for t
hese kinds of pharmaceutical analyses is therefore warranted and showed int
eresting possibilities for future applications.