Background & Objective: The presence of Lewis acid sites on the metal oxides is responsible
for a problematic elution of Lewis bases from these stationary phases due to the ligand exchange. The
interactions are quite strong and the kinetics is relatively slow which is chromatographically undesirable.
On the other hand, the interactions based on ligand-exchange could be employed in the solid-phase extraction.
We newly tested these presumptions in the extraction process of ibuprofen (Lewis base) from hydrophobic
suppositories as well as a hydrophilic oral suspension.
Method & Results: The pharmaceutical formulation was dissolved in hexane (suppositories) or 50 %
methanol (oral suspension) and 0.5 mL of the appropriate solution was loaded on a cartridge containing
bare zirconia. After washing with methanol and water, ibuprofen was eluted by 1% ammonia in methanol.
It was shown that only zirconia (in contrast to titania) was capable to extract ibuprofen from pharmaceuticals
thanks to the stronger ligand exchange properties. A novel method for ibuprofen extraction using
zirconia was proposed. The recoveries of ibuprofen were 95 % and 94 % from suppositories and an oral
Conclusion: This paper describes the first successful utilization of ligand exchange process on zirconia
in the extraction of ibuprofen from two different pharmaceuticals. It was shown the pivotal role of interactions
between the carboxylic moiety and the Lewis acid sites on the zirconia surface. The procedure can
be applied in case that the vehicle is not compatible with the chromatographic conditions used for the
subsequent analysis of the active compound.
Keywords: Ibuprofen, zirconia, titania, solid-phase extraction, pharmaceuticals, suppository, oral suspension.
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