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.