Determination of isoniazid in human urine using screen-printed carbon electrode modified with poly-L-histidine

A sensitive voltammetric method for trace measurements of isoniazid (INZ) in synthetic human urine sample is described. The method is based on its electroreduction at -0.98 V vs. Ag/AgCl on screen-printed carbon electrode (SPCE) modified with poly-L-histidine (PH). A film of good adherence on SPCE and electrocatalytic properties was obtained coating the electrode by histidine monomer electropolymerization process (SPCE/EPH). The electrochemical behavior of the modified SPCE was investigated by cyclic, linear sweep (LSV), differential pulse (DPV). square-wave voltammetry (SWV), and electrochemical impedance spectroscopy (EIS). Limits of detection of 5.0 x 10(-7) mol L-1, 1.7 x 10(-7) mol L-1 and 2.5 x 10(-7) mol L-1 were estimated from LSV, DPV and SWV determinations, respectively. The method was successfully applied to the determination of INZ in human urine samples. (c) 2009 Elsevier B.V. All rights reserved.