Rapid and selective method for quantitation of metronidazole in pharmaceuticals. 
A selective and highly sensitive assay for N-1-substituted nitroimidazoles has been modified and adapted for rapid estimation of metronidazole in pharmaceuticals.  The color reaction is based on diazotization of sulfanilamide with the nitrite ions liberated by alkaline hydrolysis of metronidazole and subsequent coupling of the diazonium salt with N-1-(naphthyl)-ethylenediamine dihydrochloride.  This method is applicable for the assay of benzoyl metronidazole in oral suspension.  Officially recommended excipients and preservatives do not interfere.