Voltammetric determination of thiomersal with a new modified electrode based on a carbon paste electrode decorated with La₂O₃

A carbon-paste modified electrode decorated with La₂O₃ (LaO_x/CPE) is reported for the first time for the voltammetric determination of thiomersal (THM) content. The LaO_x/CPE surface was characterized using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The presence of La₂O₃ on the surface of the carbon paste reduces the charge transfer resistance and improves the sensitivity toward the oxidation of THM, with an oxidation current increase of almost 60% and allows its determination by square-wave stripping voltammetry (SWSV). The detection limit (3σ/b) was 0.09 μmol L⁻¹ and the relative standard deviation was 2.5% (n = 7) with three different electrodes. Furthermore, the new sensor was applied in the detection of THM in vaccines and pharmaceutical dosages.