Simultaneous differential pulse voltammetric determination of L-dopa and carbidopa in pharmaceuticals using a carbon paste electrode modified with lead dioxide immobilized in a polyester resin

Abstract

A carbon paste electrode modified with lead dioxide immobilized in a polyester resin has been developed for simultaneous differential pulse voltammetric determination of L-dopa and carbidopa in pharmaceutical formulations. The analytical curves were linear in the concentration ranges from 2.6 ´ 10-4 to 1.2 ´ 10-3 mol L-1 and from 3.2 ´ 10-5 to 1.5 ´ 10-4 mol L-1 for L-dopa and carbidopa, respectively. The detection limits were 2.5 ´ 10-5 mol L-1 and 3.7 ´ 10-6 mol L-1 for L-dopa and carbidopa, respectively and recoveries of L-dopa and carbidopa from two samples ranged from 98.1 to 103% of the added amount. The relative standard deviations were lower than 2.5% for 1.2 ´ 10-4 and 1.2 ´ 10-3 mol L-1 of these catecholamines solutions and the results obtained for L-dopa and carbidopa in pharmaceutical formulations using the proposed voltammetric procedure are in close agreement with the labeled values and/or those obtained using an enzymatic method at the 95% confidence level.