Voltammetric determination of pyridoxine (Vitamin B6) at a carbon paste electrode modified with vanadyl(IV)-Salen complex

The preparation and electrochemical characterization of a carbon paste electrode modified with the NN-ethylene-bis(salicylideneiminato) oxovanadium(IV) complex [VO(Salen)] as well as its behaviour in relation to the oxidation of pyridoxine (Vitamin B-6) are described. The electrochemical behaviour of the modified electrode and the electrooxidation of pyridoxine were investigated using cyclic voltammetry. The best voltammetric response was obtained for an electrode composition of 15% (m/m) [VO(Salen)] in the paste, KCI solution of pH 5.5-8.0 and scan rate of 25 mV s(-1). A sensitive linear voltammetric response for pyridoxine was obtained in the concentration range of 4.5 x 10(-4) to 3.3 x 10(-3) mol 1(-1) with a slope of 42.5muA mol 1(-1)1, and a detection limit (3sigma/slope) of 3.7 x 10(-5) mol 1(-1) using linear sweep voltammetry. Among several compounds tested only Vitamin B, seems to interfere in the analyte signal. The concentrations of pyridoxine in pharmaceutical formulations using the proposed electrode and an official spectrophotometric method based in the reaction with N,N-diethyl-p-phenylenediamine are in agreement at the 95% confidence level and within an acceptable range of error. (C) 2003 Elsevier B.V All rights reserved.