Enantioselective adsorption of (+)-(S)-Naproxen in a crosslinked lipase in organic solvents

Enantioselective adsorption of (+)-(S)-naproxen from the racemate in cyclohexane, n-hexane, n-heptane, or isooctane, but not in a less hydrophobic solvent such as toluene, was obtained by using a crosslinked lipase (ChiroCLEC-CR) as the adsorbent. However, this behavior was not observed in cyclohexane when a crude lipase, a purified lipase, or the crosslinked lipase preexposed to the organic solvent for 24 hours was employed. Effects of racemic naproxen concentration and solvent hydrophobicity on the amount of enantiomer adsorbed to the adsorbent, the partition coefficient (i.e., the ratio of enantiomer concentration in the adsorbent to that in the organic solvent), and the selectivity factor [i.e., the ratio of partition coefficients for (+)-(S)- and (-)-(R)-naproxen] were determined. Moreover, desorption of the enantiomer from the absorbent was compared when a fresh organic solvent was substituted or a displacer such as steric acid was added to the solution after the adsorption operation.