Simultaneous high-performance liquid chromatographic stability-indicating analysis of acetaminophen and codeine phosphate in tablets and capsules.

A high-performance liquid chromatographic method has been developed for the simultaneous determination of acetaminophen and codeine phosphate for product stability studies, and release and dissolution testing of tablets and capsules. The reversed-phase method utilizes UV detection at 214 nm, a C18 column and requires a maximum of 10 min per analysis. The method has been validated for use with products containing as much as 500 mg of acetaminophen and as little as 7.5 mg of codeine phosphate. The known potential degradation products, p-aminophenol, codeine N-oxide, and codeinone are separated for quantitation simultaneous with the parent compounds. The method has been shown to be linear, reproducible, specific, sensitive and rugged.