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A quantitative method for the assay of phenol in ointments is described. The procedure involves the formation of a blue indophenol by reacting phenol with 2,6-dibromoquinone-4-chloroimide which can be measured spectrophotometrically. The method is accurate, and interference from other active ingredients (hydrocortisone and menthol) does not occur.

The development of a simple, shorter and more accurate method than the NF method for the determination of benzyl benzoate in Benzyl Benzoate Lotion NF is discussed. Hydrolyzed benzyl benzoate was measured spectrophotometrically. Interference from other ingredients of the lotion, oleic acid and triethanolamine was almost negligible. The proposed method was completed in approximately 15 minutes, as opposed to the two hours required by the NF procedure.

Three techniques--ultraviolet, high pressure liquid chromatography (HPLC) and acid dye--were compared as stability-indicating assay methods. Investigations on six drugs (codeine phosphate, ephedrine hydrochloride, morphine sulfate, procaine hydrochloride, pyrilamine maleate and thiamine hydrochloride) indicate that HPLC is the most reliable method.

A simplified method for the quantitative analysis of hyoscyamine hydrobromide or atropine in Belladonna Tincture USP is described. The procedure is based on the formation of an alkaloid-dye complex which can be extracted with an organic solvent and measured spectrophotometrically. The results obtained by this method compare favorably with those obtained by the USP method.