Thermodynamic Study of Racemic Ibuprofen Separation by Liquid Chromatography Using Cellulose-Based Stationary Phase

Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID), also known for its significant antipyretic and analgesic properties. This chiral drug is commercialized in racemic form; however, only S-(+)-ibuprofen has clinical activities. In this paper the effect of temperature change (from 288.15 to 308.15 K) on the ibuprofen resolution was studied. A column (250×4.6 mm) packed with tris(3,5-dimethylphenylcarbamate) was used to obtain the thermodynamic parameters, such as enthalpy change (ΔH), entropy change (ΔS), variation enthalpy change (ΔΔH), variation entropy change (ΔΔS), and isoenantioselective temperature (Tiso). The mobile phase was a combination of hexane (99%), isopropyl alcohol (1%), and TFA (0.1%), as an additive. The conditions led to a selectivity of 1.20 and resolution of 4.55. The first peak, R-(−)-ibuprofen, presented an enthalpy change of 7.21 kJ/mol and entropy change of 42.88 kJ/K·mol; the last peak, S-(+)-ibuprofen, has an enthalpy change of 8.76 kJ/mol and 49.40 kJ/K·mol of entropy change.