Indirect Electrochemical Determination of Carvedilol through its Interaction with Nitrous Acid

An indirect electrochemical determination of carvedilol (CAR) as pure and in its pharmaceutical tablets through its interaction with nitrous acid has been studied using square wave voltammetry (SWV). Nitrous acid which is prepared instantaneously in a voltametric cell contains a three-electrodes detection system, a glassy carbon electrode (GCE) as the working electrode, Pt-wire as an auxiliary electrode and silver/silver chloride/ saturated potassium chloride (Ag/AgCl. sat. KCl) as a reference electrode, gives a well-defined oxidation peak at 1.35 V vs. Ag/AgCl. saturation KCl. The effect of different pH (buffer types), time and concentration were tested. The calibration curve was constructed under measured optimum conditions by following the decrease in nitrous acid peak as a result of the addition of carvedilol solution. The plot of carvedilol concentration added and the differences in current gives two straight lines, first at a low concentration range (0.499 -5.99) 10-8 M by a calibration equation Y=93.893x-4.9093 and second, at a high concentration range (6.99 - 11.98) 10-8 M by a calibration equation Y=9.2363x+484.69 with correlation coefficient R2 equal 0.9937 and 0.9574 respectively. The limit of detection (LOD) was (0.1004810-8) M and the limit of quantitation (LOQ) was (0.33493 10-8) M.