A mechanistic study to provide diagnostics of anodic stripping electrode processes at bismuth-film electrodes is presented from both theoretical and experimental points of view. Theoretical models for three types of electrode mechanisms are developed under conditions of square-wave voltammetry, combining rigorous modeling based on integral equations and the step function method, resulting in derivation of a single numerical recurrent formula to predict the outcome of the voltammetric experiment. In the course of the deposition step, it has been assumed that a uniform film of the metal analyte is formed on the bismuth substrate, in situ deposited onto a glassy carbon electrode surface, without considering mass transfer within either the bismuthor the metal analyte film. Theoretical data are analyzed in terms of dimensionless critical parameters related with electrode kinetics, mass transfer, adsorption equilibria, and possible lateral interactions within the deposited metal particles. Theoretical analysis enables definition of simple criteria for differentiation and characterization of electrode processes. Comparing theoretical and experimental data, anodic stripping processes of zinc(II), cadmium(II), and lead(II) are successfully characterized, revealing significant differences in their reaction pathways. The proposed easy-to-perform diagnostic route is considered to be of a general use while the bismuth film exploited in this study served as a convenient nonmercury model substrate surface
COBISS.SI-ID: 4942874
Antimony film electrode (SbFE) prepared in-situ is presented for the first time in combination with adsorptive cathodic stripping regime for measuring trace levels of Ni(II). Stabilization of Sb(III) in mildly alkaline solution (pH 9.0) was achieved through the addition of potassium sodium tartrate in themeasurement solution, and as a complexing agent for Ni(II) dimethylglyoximewas selected. The SbFE exhibited excellent electroanalytical performance in the presence of dissolved oxygen with a calculated LoD of 0.11 Žg LŽ1 Ni(II) in combination with 60 s accumulation time and favorable linear response in the examined concentration range of 2-20 Žg LŽ1 (R2=0.998) associated with only 20 s accumulation. The electrode revealed superior performance over its ex-situ prepared analogue and, furthermore, exhibited auspicious electroanalytical performance also under constant current chronopotentiometric conditions
COBISS.SI-ID: 4942618
In collaboration with our partners from China we conducted an investigation on the preparation and characterization of a nano-hybrid microprobe, composed of carbon nanotube-modified carbon fibre coated with gold nanoparticles (GNPs) attached to a polymer film, which was reported for the first time. The functionalization of the microelectrodes with polymer film prior to the GNP attachment step was demonstrated to significantly improve the GNP surface coverage and distribution. Surface status characterization of these hybrid structured electrodes was performed using scanning electron microscopy. By using cyclic voltammetry, possible application of the proposed nano-composite microprobe for enzymeless glucose detection was demonstrated.
COBISS.SI-ID: 5149978
Nitrogen-containing organic compounds in the atmosphere have drawn attention owing to their impact on aerosol chemistry and physics and their potential adverse effects on the biosphere. Among them, nitrocatechols and their homologs have recently been associated with biomass burning. In the present study, nitrocatechols, nitrophenols, nitroguaiacols and nitrosalicylic acids (NSAs) were simultaneously quantified for the first time by using a new analytical method based on liquid chromatography/tandem mass spectrometry, which was systematically optimized and validated. Several analyte specific issues regarding the sample preparation and chromatographic analysis were addressed in order to ensure method sensitivity, precision, and accuracy. Sample matrix effects were thoroughly investigated in order to ensure method specificity. The method was found to be sensitive with limits of detection ranging from 0.1 to 1.0 microg L-1, and with accuracy generally between 90 and 104%. The relative standard deviations for repeatability and intermediate precision were better than 4% and 9%, respectively. The method was applied to the analysis of winter and summer PM10 samples from the city of Ljubljana, Slovenia. Aerosol concentrations as high as 152 and 134 ng m-3 were obtained for the major aerosol nitro-aromatics: 4-nitrocatechol (4NC) and methyl-nitrocatechols (MNCs), respectively. Up to 500-times higher concentrations of 4NC and MNCs were found in winter compared to summer aerosols. The correlation analysis for winter samples showed that 4NC, MNCs, and NSAs are strongly inter-correlated (R2 = 0.84-0.96). Significant correlations between these analytes and anhydrosugars support their proposed origin from biomass burning. The studied nitro-aromatics were found to constitute a non-negligible fraction (around 1%) of the organic carbon.
COBISS.SI-ID: 5115418
We prepared a new method for extraction of phenols from olive oil using ultrasonication and freezing of methanol extract as fat removal step. Comparison to conventional methods, our method gives sufficient recoveries and is quicker and environmental friendly since it does not contain a usual fat removal step with hexane.
COBISS.SI-ID: 2250235