Colorimetric analytical study of oxyphenbutazone

A procedure was developed for the colorimetric determination of oxyphenbutazone by treatment with dilute nitrite and dilute hydrochloric acid solutions for 10 min, then rendering alkaline with potassium hydroxide. By this simple colorimetric measurement, quantities of oxyphenbutazone from 2.5 to 10 mg/100 ml are determined with an accuracy of 98.80 +/- 1.33%. Application of the suggested method to different pharmaceutical preparations has shown no significant difference compared with the Brit. Ph. 1980 method. A colour reaction mechanism is discussed.