Indirect kinetic-spectrophotometric determination of resorcinol, catechol,and hydroquinone

A rapid, simple, and sensitive method for the determination of trace amount s of resorcinol, catechol, and hydroquinone in aqueous media has been propo sed. The method is based on their reaction with nitrite. The excess nitrite is then determined by a kinetic method based on its reaction with Neutral Red. The reaction is monitored spectrophotometrically by measuring the decr ease in the absorbance at 530 nm by a fixed time method. Resorcinol, catech ol, and hydroquinone could be determined by the proposed method in the rang es of 0.1-2.0 mg/mL, 0.25-2.0 mg/mL and 0.1-3.0 mg/mL, respectively. The me thod was applied to the determination of resorcinol and catechol in pharmac eutical formulations with satisfactory results.