The electrochemical reduction and adsorption of todralazine on the hanging mercury drop electrode are explored. These properties allow the development of a sensitive adsorptive stripping voltammetric procedure, with a detection limit of 3.2 x lo-' mol L-'. A method is proposed for rapid determination in commercial preparations and human serum.
IhTRODUCTIONTodralazine is a substance with antihypertensive properties used extensively in pharmaceutical preparations. There are numerous reports in which voltammetric techniques have been used in the determination of similar substances [l-51. Todralazine is a benzodiazine with the following structure:
NHNIICOOCJfi
IThe presence of azometine reducible groups (kN-) on the hanging mercury drop electrode (HMDE) can be used for the electroanalytical determination of todralazine. This process has been used by others to determine compounds of biological interest such as triazinic herbicides [6] or benzodiazepines [7][8][9][10][11].Other techniques have been used to determine todralazine. For example, Ishii and Deguchi [12] proposed a spectrofluorimetric technique for its determination in plasma. Todralazine hydrochloride has also been determined using a selective chloride electrode or by indirect potentiometric titration with a silver electrode [ 131. Kracmar et al. [ 141 employed LJV spectrophotometry for the determination of this substance.This article explores the reductive and adsorption processes of todralazine, toward the development of a highly sensitive adsorptive stripping voltammetric (AdSV) procedure for measuring this drug.' To whom correspondence should be addressed 0 1 9 1 VCH Publishers, Inc.
mmm-'Apparatus A multifunctional electroanalytical system consisting of a Metrohm E-506 Polarecord, an E-612 scanner, a VA-663 unit stand, and an X Y Linseis LY-1800 register were used for the cyclic voltammetric studies. A Metrohm VA-646 processor coupled to a VA-646 unit stand was also used, which, as in the above, incorporated a Metrohm Multimode 6.1246.020 as the working electrode, an Ag/AgCl reference electrode, and a platinum auxiliary electrode. A Metrohm E-605 pH-meter was used to measure the pH.
ReagentsThe todralazine stock solution (Sigma), 1.25 X lo-' mol L-I, was prepared in distilled and deionized water. A Britton-Robinson buffer solution containing 0.04 mol L-' of each acid component was used as supporting electrolyte. All reagents used were of analytical grade. Aperdor (Tanabe) tablets were used as representative samples. The human serum samples were pools from five subjects.
ProcedureDetermination of Todraluzine in Pharmaceutical Prqaratim. The content of a capsule was transferred quantitatively to a 100 mL calibrated flask and diluted to volume with water. An aliquot of the solution (10 mL) was transferred to the 100 mL calibrated flask, and 10 FL of an aliquot of this solution was diluted to 25 mL with Britton-Robinson buffer (pH 1.90) and transferred to the polarographic cell.Determinution of Todralazine in Human Serum. First 2 mL of ethanol ...
