Optical purity determination of (S)-ibuprofen in tablets by achiral gas chromatography

An optical purity test was indirectly performed on (S)-ibuprofen as its diastereomeric (R)-(+)-1-phenylethylamide derivative using achiral gas chromatography (GC). The method for the determination of trace (R)-ibuprofen (optical impurity), within the range 1.0 to 50 ng, from a racemic ibuprofen standard was linear (r = 0.9997) with acceptable precision (% RSD < or = 5.3) and accuracy (% RE = 0.7 - -3.9). Similar results were obtained with the method validation for the quantification of (S)-ibuprofen within the range 0.1 to 2.0 microg using a (S)-ibuprofen standard. When applied to seven different commercial (S)-ibuprofen products, their optical purities (98.7 - 99.1%) were determined with good precision (% RSD < or = 4.0).