Determination of enantiomeric composition of ibuprofen in bulk drug by proton nuclear magnetic resonance spectroscopy with a chiral lanthanide chelate.

The enantiomeric composition of ibuprofen was determined in a simple and reliable manner by proton nuclear magnetic resonance spectroscopy with a chiral lanthanide chelate. Optimum complexation with the europium (III) chelate took place in CCl4 after conversion of the enantiomeric sample into a mixture of methyl esters. The optimization of the experimental conditions in terms of substrate concentration and lanthanide chelate to substrate molar ratio led to two sets of signals of utility for quantitative purposes. Analysis of synthetic enantiomeric mixtures by the proposed method demonstrated excellent agreement between the assay results and the known masses of each enantiomer present in the mixture samples. The average +/- S.D. recovery values were 99.39 +/- 0.92 and 99.42 +/- 0.68% (n = 10) of (S)-(+)-ibuprofen depending on whether the quantitation was based on the alpha-methyl protons or ester methyl protons, respectively.