Determination of metabolites of 3-chloro-4-benzyloxyphenylacetic acid (benzofenac) by GC/MS method.

Metabolites of benzofenac (3-chloro-4- benzyloxyphenylacetic acid) were determined in rat, rabbit, dog, and human urine by GC/MS. Before analysis the urine was extracted and the extracts were treated with diazomethane. Deuterium-labelled benzofenac , 3-chloro-4-[( methylene-2H2]- benzolyoxy ) phenylacetic acid was used for the elucidation of the structures of some main metabolites and the determination of trace metabolites. The structures of the metabolites were determined from spectra obtained by electron impact and chemical ionization.