A new kinetic spectrophotometric method for the determination of hydroxyl radical produced from the decomposition of peroxynitrite was proposed, based on the hydroxyl radical reacting with benzoic acid to produce hydroxyl benzoic acid and the hydroxyl benzoic acid can inhibite the reaction of Mn(III) oxidizing arsenious acid catalyzed by iodide. The indirect determination of hydroxyl radical can be done through the kinetic spectrophotometric method for the measurement of hydroxyl benzoic acid. The method proposed is sensitive and simple. The method has been used to determine the yields of hydr...