Robert Piech

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

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.

Fast and sensitive metronidazole determination by means of voltammetry on renewable amalgam silver-based electrode without the preconcentration step

Application of cyclic renewable amalgam silver-based electrode (Hg(Ag)FE) for sensitive metronidazole detection by the differential pulse voltxadammetry (DPV) is described. The unique properties of the Hg(Ag)FE such as the relative large surface area and its fast and very simple renewal were fully utilized for sensitive measurements. Compared with the classical hanging merxadcury drop electrode (HMDE), the renewable Hg(Ag)FE significantly increases the reduction peak current of metronidazole because of its large surface area. The effects of various factors for the metronidazole determination such as: pulse height and width, step potential, surface area of the working electrode, and basic electrolyte composition are optimized. The obtained calibration graph is linear from 0.1 (17 μgxa0L -1 ) to 2 µM (342 μgxa0L -1 ) with correlation coefxadficient 0.999. For the Hg(Ag)FE with the surface area of 10.1 mm 2 the limit of detection ( LOD ) is 20 nM (3.4xa0μgxa0L -1 ). The repeatability of the method at a concentration of the analyte of 0.5 µM (5.6xa0μgxa0L -1 ), expressed as relative stanxaddard deviation ( RSD ) is 2.1 % ( n = 7). The proposed method was successfully applied and confirmed by studying recovery of metronidazole from spiked samples.