Thiomersal determination on a renewable mercury film silver-based electrode using adsorptive striping voltammetry

Abstract

Thiomersal(ethyl(2-mercaptobenzoato-(2-)-O,S)mercurate(1-)sodium) is an organic mercury compound, containing 49.8% mercury in its composition, commonly used as a preservative in cosmetics and pharmaceutical products. In this work differential pulse adsorptive stripping voltammetry (DP AdSV) is applied for thiomersal determination using a renewable mercury film electrode Hg(Ag)FE. The effects of various factors were optimized such as: preconcentration potential and time, step potential, pulse height and electrolyte composition. A linear voltammetric response was obtained for the analyte in the concentration range from 2 nmol L⁻¹ (0.81 μg L⁻¹) to 0.2 μmol L⁻¹ (81.0 μg L⁻¹), with a detection limit of 0.9 nmol L⁻¹ for a preconcentration time of 90 s. The repeatability of the method at a concentration level of thiomersal equal to 0.025 μmol L⁻¹, expressed as RSD is 2.2% (n = 10). The proposed method was successfully applied for thiomersal determination in different vaccines. The method was validated by studying the recovery of thiomersal from vaccine samples.