Colorimetric determination of terbutaline sulfate and orciprenaline sulfate via nitrosation and difference spectrophotometry.

A colorimetric method is proposed for determination of terbutaline sulfate, orciprenaline sulfate, and their dosage forms. The suggested method depends on nitrosation of the 2 drugs by using sodium nitrite and hydrochloric acid. Addition of sodium hydroxide increases the intensity of the color developed. The difference between absorption values measured in acid and alkaline media is taken as a measure of concentration. Variables were carefully studied and optimized. Results for both compounds adhered to Beer's law over the range 2-28 micrograms/mL. The method has proved to be accurate and precise for analysis of pharmaceutical dosage forms.