Voltammetric determination of phenylbutazone and oxyphenbutazone at a glassy carbon electrode

Linear-sweep and differential-pulse voltammetric methods are reported for the determination of phenylbutazone and oxyphenbutazone and of their pharmaceutical dosage forms. The methods are based on the electrochemical oxidation of phenylbutazone and oxyphenbutazone at a glassy carbon electrode in 0.1 M sodium acetate—0.1 M acetic acid in 98% ethanol. The mechanisms are discussed. The proposed methods show good reproducibility and are not subject to interference from common tablet excipients and from possible therapeutically active drug substances used in combination with phenylbutazone and oxyphenbutazone. A simple interrupted-sweep procedure can be used to determine phenylbutazone in the presence of oxyphenbutazone.