A ccurate and simple spectrophotometric method has been suggested for the determination of oxymetazoline hydrochloride (OMCl) in aqueous solution is developed. The present process included coupling of OMCl with diazotized sulphanilic acid reagent in the presence of sodium hydroxide. The orange colored azo dye formed very stable and soluble in water gives maximum absorption at 496 nm. The lineratey is obeyed over the range 20-400 g / 25 ml (0.8-16µg.ml-1) the molar absorptivity is equate to 2.30  10 4 l.mol-1 cm-1. The proposed method has been used to the determination of OMCl in two formulations with satisfactories results.

Two simple and sensitive visible spectophotometric methods have been developed for the quantitative determination of mesalazine (MEZ) in bulk drug and pharmaceutical preparation (capsules). The proposed methods are based on oxidative coupling reaction of mesalazine with 8-hydroxyquinoline (method A) and N-(1-naphthyl)ethylendiamine (N-NED) (method B) in the presence of sodium periodate as oxidizing agent in alkaline medium to form coloured products, exhibiting maximum absorptions at 644 nm and 543 nm, respectively. Beer ' s law was obeyed in the concentrations range of 10-300 and 10-180 µg /25ml with molar absorptivity of 1.7223×10 4 and 0.6545×10 4 l.mol-1 cm-1 , respectively. The relative error ranged between-0.4% to +0.16% and-0.9% to-0.31% with relative standard deviation of ±1.31% to ±0.39% and ±0.88% to ±0.32% for methods A and B, respectively. The optimum conditions for full colour development are described and the proposed methods were applied successfully to the assay of MEZ in pharmaceutical preparation (capsules).