GLC assay for fenclorac.

A rapid stability-indicating GLC method is described for the determination of fenclorac as the diethylamine salt in dosage formulations. The procedure is also applied in detecting and quantitating the weight percent of 3-chloro-4-cyclohexylphenylglycolic acid and alpha-chloro-4-cyclohexylphenylacetic acid impurities associated with the synthesis of the fenclorac drug substance. The former compound, in addition to being an impurity, is also the degradation product of fenclorac. The procedure involves preparations of the silyl derivatives, addition of an internal standard (triphenylethylene), and use of a hydrogen flame-ionization detector. The column, with a phenyl methyl silicone liquid phase and operated at about 195degrees, is well suited for the separation. The silyl derivatives were characterized by GLC-mass spectrometry.