Determination of azobenzene and hydrazobenzene in phenylbutazone and sulfinpyrazone products by high-performance liquid chromatography.

A high-performance liquid chromatographic method has been developed for the simultaneous determination of azobenzene and hydrazobenzene in phenylbutazone and sulfinpyrazone raw materials and formulations. The drug raw material or formulation is shaken with 1N NaOH and n-hexane and centrifuged. The n-hexane layer is injected into a chromatograph equipped with a 10-micron cyano-amino bonded phase column. Azobenzene and hydrazobenzene are detected at 313 and 254 nm, respectively; the sensitivities are approximately 1 and 2 ppm, respectively, in the raw materials and formulations.