Thermodynamic and Kinetic Study of Chiral Separation of Some Non-Steroidal Anti-Inflammatory Drugs on Dinitrobenzamido Tetrahydrophenanthrene Stationary Phase

Document Type : Original Article

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Pharmaceutical Analytical Chemistry Department, Faculty of Pharmacy, Tanta University, Tanta 31111, Egypt

Abstract

The chiral separation of three arylpropionic acid-based non-steroidal anti-inflammatory drugs: ibuprofen, ketoprofen and ketorolac is thermodynamically and kinetically studied on dinitrobenzamido tetrahydrophenanthrene (Whelk-O 2) stationary phase in the reversed phase mode. This study aims to investigate the chromatographic behavior of these compounds on Whelk-O 2 and to better understand this stationary phase and the mechanistic details of its chiral recognition. Statistical moments are used to calculate thermodynamic and kinetic parameters. The thermodynamic study shows that upon increasing temperature from 15 to 35 °C, both retention and enantioselectivity decrease and the enantioseparation process is enthalpy-controlled. The retention mechanism is independent of temperature and no conformational changes occur in the Whelk-O 2 phase as indicated by the linear van’t Hoff plots. The investigated drugs have the same retention mechanism on Whelk-O 2 as demonstrated by the linear enthalpy-entropy compensation plots. The chiral recognition mechanism involves π-π interaction and hydrogen bonding with ibuprofen having the strongest interactions. The kinetic study involves the investigation of sorption and desorption rate constants using Arrhenius plots. The rate of sorption is always greater than the rate of desorption for the three drugs. Ibuprofen has sharper peaks and shorter retention time compared to ketoprofen and ketorolac due to its faster rates and lower activation energy of sorption and desorption.

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