Electrochemical behavior and voltammetric determination of pyrazinamide using a poly-histidine modified electrode

Pyrazinamide (Pyrazinecarboxamide - PZA) is a drug that is used to treatment tuberculosis. In the present work, the voltammetric behavior of PZA was studied using a screen-printed modified electrode (SPCE). The modified electrode was constructed using poly-histidine films, and it showed an electrocatalytic effect, thus promoting a decrease in PZA reduction potential and improving the voltammetric response. Cyclic voltammetry and electrochemical impedance spectroscopy techniques have been employed in order to elucidate of the electrodic reaction. The results allowed the proposal that in the PZA reduction, a further chemical reaction occurs that corresponds to a second-order process which is subsequent to the electrode reaction. In addition, a sensitive voltammetric method was developed, and it was successfully applied for PZA determination in human urine samples. The best response was found using SPCE modified with poly-histidine prepared by histidine monomer electropolymerization (SPCE/EPH). The electroanalytical performance of the SPCE/EPH was investigated by linear sweep (LSV), differential pulse (DPV), and square wave voltammetry (SWV). A linear relationship between peak current and PZA concentrations was obtained from 9.0 x 10(-7) to 1.0 x 10(-4) mol L-1 by using DPV. The limit of detection at 5.7 x 10(-7) mol L-1 was estimated, and a relative standard deviation of the 5.0 x 10(-6) mol L-1 of PZA of 10 measurement was 3.7%. (C) 2012 Elsevier B.V. All rights reserved.