4-Phenyl isothiocyanate modified electrode based on diazonium electrodeposition for heavy metals detection in pharmaceuticals

A stable layer of 4-phenyl isothiocyanate (4-PITC) was successfully electrografted on glassy carbon electrode (GCE). The electrode modification process was performed in three sequential steps in a single solution: (1) reduction by chronoamperometry of the nitro groups of 4-NITC to amino moieties (2) in situ reaction of amino with nitrous acid to obtain unstable diazonium functional groups and (3) electrografting by chronopotentiometry of diazonium. A thin optimal layer with minimum surface fouling was obtained. The formation of the organic film was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrode was used for detection of Pb(II) and Fe(II) by differential pulse voltammetry (DPV). Under optimal conditions, the limit of detection 1.2 μg L^-1 for Pb(II) and of 2.0 μg L^-1 for Fe(II) were achieved. The developed electrode was successfully applied to detect Pb(II) and Fe(II) in injectable iron pharmaceuticals used to treat iron deficiency anemia simultaneous with investigation of contamination by Pb(II).