Beata Paczosa-Bator

Diagnostic of functionality of polymer membrane – based ion selective electrodes by impedance spectroscopy

Electrochemical impedance spectroscopy (EIS) is a powerful tool for the analysis of various electrochemical systems because it allows the separation and characterization of individual kinetic processes. In this paper we investigate whether changes in the EIS characteristics can be used to distinguish between solid-state ISE membrane that have been subjected to physical damage, biofouling or leaching of active components. We conclude that with these relatively simple electronic measurements, we can effectively evaluate the functionality of the ISE membrane; i.e. we can predict whether the sensors are fully functional, in need for calibration or are completely non-functional. We believe this could form the basis of a simple but effective diagnostic tool for probing the condition of remotely deployed ISEs in widely distributed chemo-sensor networks (e.g. for environmental monitoring) and for enhancing the reliability of these devices. Our ultimate goal is to implement such tools in place of conventional approaches to ISE testing like calibration with standard solutions, which require the integration of complex and costly fluidics.

Effects of type of nanosized carbon black on the performance of an all-solid-state potentiometric electrode for nitrate

AbstractThe potentiometric properties of all-solid-state nitrate-selective electrodes based on plasticized PVC and containing different types of nanosized carbon black were investigated. The use of a carbon black interlayer is shown to significantly improve the potentiometric response. The electrodes display a close-to-Nernstian slope in the range from 10−1 to 10−6xa0M, highly stable potentials and low membrane resistance. However, different analytical features were found depending on the type of carbon black used. The best long-term potential stability was observed for the electrode with Printex XE2-B carbon black that has a relatively high BET surface area (1000xa0m2u2009·u2009g−1) and an average particle size of 30xa0nm. Nevertheless, the electrodes with the Vulcan XC-72 (BET surface: 240xa0m2u2009·u2009g−1; average size: 55xa0nm) showed the most repeatable and reproducible standard potential. The lowest detection limit for nitrate (2.5·10−7 M) is observed for an electrode containing Vulcan XC-72.n FigureThe comparison of the potentiometric behavior of all-solid state ion-selective electrodes with the different types of the furnace carbon black is presented by employing the nitrate-selective membrane. The electrodes display a close-to-Nernstian slope, highly stable potentials and low membrane resistance

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.