Rapid, inexpensive stereoselective densitometric-thin layer chromatographic methods using vancomycin and N-acetyl-L-cysteine as chiral selectors were developed and fully validated for the enantioseparation of racemic mixtures of ketoprofen and ibuprofen and quantitative determination of their chiral switching (eutomer) isomers dexketoprofen tromethamol and dexibuprofen. The effect of different chiral selector types, concentration, temperature and pH on the chiral resolution was investigated. The spots were detected using UV lamp followed by densitometric measurements at 255 nm and 265 nm for dexketoprofen tromethamol and dexibuprofen, respectively. The mobile phases enabling successful resolution were methanol:1% diethylamine (5:5 v/v, pH 6) using vancomycin for rac-ketoprofen and ethyl acetate:methanol:distilled water containing 40 mg N-acetyl-L-(+)-cysteine:triethylamine (6:2:2:1.2 v/v, pH 10) for rac-ibuprofen. The thermodynamic parameters enthalpy ΔH and entropy ΔS were investigated to study the effect of temperature on the enantioseparation using Van’t Hoff plot. The limits of detection and quantifications were 0.215 and 0.651, and 2.560 and 7.750 for dexketoprofen and dexibuprofen, respectively.
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