Solvent Versatility of Immobilized Amylose and Cellulose-Based Chiral Stationary Phases in Enantioselective LC Separation and Monitoring of Bio-Catalyzed Resolutions of Acidic Drugs in Non-Standard Organic Solvents Ashraf Ghanem 1,& , Mohammed Nabil Aboul-Enein 2 , Aida El-Azzouny 2 , Mohammed F. El-Behairy 2 1 Australian Centre for Research on Separation Science, School of Chemistry, University of Tasmania, Private Bag 75, Hobart, TAS 7001, Australia; E-Mail: aghanem@utas.edu.au 2 Medicinal and Pharmaceutical Chemistry Department, Pharmaceutical and Drug Industries Research Division, National Research Centre (NRC), Dokki-Cairo, Egypt Dedicated to Professor Paul Haddad on the Occasion of his 60th Birthday. Received: 11 February 2009 / Revised: 22 April 2009 / Accepted: 29 May 2009 Online publication: 16 July 2009 Abstract The solvent versatility of Chiralpak IA (amylose tris(3,5-dimethylphenylcarbamate)), Chiralpak IB (cellulose tris(3,5-dimethylphenylcarbamate)) and Chiralpak IC (cellulose tris(3,5-dichlorophenylcarbamate)) immobilized onto silica gel, are investigated for the enantioselective separation of a set of acidic drugs in liquid chromatography. Non-standard LC organic solvents like dichloromethane, ethyl acetate, tetrahydrofuran, methyl-tert-butyl ether were used in mobile phase compositions and/or diluent agent for the analyte on all new columns. Furthermore, the enantioselective separations of the reported compounds were compared on both immobilized columns (Chiralpak IA and IB) and their conventionally coated versions (Chiralpak AD-H and Chiralcel OD-H, respectively), using a mixture of n-hexane/2-PrOH/TFA (80:20:0.1 v/v/v). The versatility of the immobilized Chiralpak IB in monitoring reactions performed in non-standard solvent was studied on a representative example consisting of the lipase-catalyzed enantioselective esterification of flurbiprofen with n-butanol in methyl-tert-butyl ether as organic solvent. Keywords Column liquid chromatography Enantioselective separation Immobilized chiral stationary phase Acidic drugs Amylose tris(3,5-dimethylphenylcarbamate) and cellulose tris(3,5-dimethylphenylcarbamate) Introduction Over the years, it has become evident that the enantiomers of numerous drugs can follow distinct pharmacodynamic and pharmacokinetic patterns [1]. Accordingly, enantioselective separation and determination of enantiomeric pur- ity of racemic compounds are essential in modern pharmaceutical industries [2–5]. Among the methods used in the deter- mination of enantiomeric purity [6–10], enantioselective liquid chromatography is known as one of the most flexible, efficient and cost-effective technique used to resolve racemic mixture [11]. The impetus for reliance on enantioselective chromatography has been fueled by re- cent advances in chiral stationary phases (CSPs) that allow reliable, robust and efficient resolution of mg to g quantities of chiral molecules in short time. Since their introduction to chiral separation, derivatized cellulose- and amylose-based CSPs have proved their usefulness as chiral selectors in both LC and capillary electrochromatography (CE). A wide range of enantiomeric 2009, 70, 349–363 DOI: 10.1365/s10337-009-1201-1 0009-5893/09/08 Ó 2009 Vieweg+Teubner | GWV Fachverlage GmbH Original Chromatographia 2009, 70, August (No. 3/4) 349