6533b853fe1ef96bd12ac973

RESEARCH PRODUCT

Effect of the hydrophobic spacer in bonded [Cu(l-hydroxyprolyl)alkyl]+ silicas on retention and enantioselectivity of α-amino acids in high-performance liquid chromatography

subject

description

Abstract The following chiral ligands were bonded to silica: [Cu( l -hydroxyprolyl)methyl) + on LiChrosorb Si 60 (1), [Cu( l -hydroxyprolyl)methyl] + on LiChrosorb Si 100 (2) and [Cu( l -hydroxyprolyl) n -octyl] + on LiChrosorb Si 100 (3). The packings contained residual iodomethyl- and ω-iodooctyl groups at the surface. Studies on packing 1 and 2 under comparable conditions in eluents containing 10 -4 M copper acetate showed a higher retention on 1 than on 2 but a much better enantioselectivity in the latter case. The retention of enantiomers on all packings examined was found to be governed by the eluent pH and methanol content as well as by the concentration of ammonium acetate. The variation of the hydrophobic spacer from methyl, to propyl and n -octyl in the bonded bis(amino acidato)copper complex permitted a sensitive control of retention and gave rise to unique changes in the enantioselectivities which are assumed to be attributable to multiple solute—surface interactions, i.e ., complexation, ion-exchange and hydrophobic interactions.