Immobilized β-cyclodextrin-based silica vs polymer monoliths for chiral nano liquid chromatographic separation of racemates

• A facile one pot synthesis of new β-CD functionalized silica monoliths.
• The new capillary columns (150 μmID) operate under reversed phase condition.
• The column is 10,000 less in ID and operates with one million time less solvent.
• 56 cpds were investigated using enantioselective nano LC under reversed phase condition.
• The column consumes less solvent and produces faster and reproducible separations.

The enantioselectivity of immobilized β-cyclodextrin phenyl carbamate-based silica monolithic capillary columns was compared to our previously described polymer counterpart. 2,3,6-Tris(phenylcarbamoyl)-β-cyclodextrin-6-methacrylate was used as a functional monomer for the preparation of β-cyclodextrin (β-CD)-based silica and polymer monoliths. The silica monoliths were prepared via the sol–gel technique in fused silica capillary followed by modification of the bare silica monoliths with an anchor group prior to polymerization with β-CD methacrylate using either 2,2′-azobis(isobutyronitrile) or benzoylperoxide as radical initiators. On the other hand, the polymer monoliths were prepared via the copolymerization of β-CD methacrylate and ethylene glycol dimethacrylate in different ratios in situ in fused silica capillary. The prepared silica/polymer monoliths were investigated for the chiral separation of different classes of pharmaceuticals namely; α- and β-blockers, anti-inflammatory drugs, antifungal drugs, dopamine antagonists, norepinephrine-dopamine reuptake inhibitors, catecholamines, sedative hypnotics, diuretics, antihistaminics, anticancer drugs and antiarrhythmic drugs. Baseline separation was achieved for alprenolol, bufuralol, carbuterol, cizolertine, desmethylcizolertine, eticlopride, ifosfamide, 1-indanol, propranolol, tebuconazole, tertatolol and o-methoxymandelic acid under reversed phase conditions using mobile phase composed of methanol and water. The silica-based monoliths showed a comparative enantioselectivity to the polymer monoliths.

Scanning electron micrograph of A2 at 500× and 25,000× respectively showing homogenous porous monolithic structure.Figure optionsDownload as PowerPoint slide