Plasma Activation of Copper Nanowires Arrays for Electrocatalytic Sensing of Nitrate in Food and Water

Electrochemical methods for nitrate detection are very attractive since they are suitable for in-field and decentralized monitoring. Copper electrodes are often used to this aim as this metal presents interesting electrocatalytic properties towards nitrate reduction. In this research, we study improvements in the electrochemical analysis of nitrate in natural water and food by taking advantage of the detection capabilities of ensembles of copper nanowire electrodes (CuWNEEs). These electrodes are prepared via template electrodeposition of copper within the nanopores of track-etched polycarbonate (PC) membranes. A critical step in the preparation of these sensors is the removal of the template. Here, we applied the combination of chemical etching with atmospheric plasma cleaning which proved suitable for improving the performance of the nanostructured copper electrode. Analytical results obtained with the CuWNEE sensor for nitrate analyses in river water samples compare satisfactorily with those achieved by standard chromatographic or spectroscopic methods. Experimental results concerning the application of the CuWNEEs for nitrate analysis in food samples are also presented and discussed, with focus on nitrate detection in leafy vegetables

Atmospheric Deposition of Inorganic Elements and Organic Compounds at the Inlets of the Venice Lagoon

The Venice Lagoon is subjected to long-range transport of contaminants via aerosol from the near Po Valley. Moreover, it is an area with significant local anthropogenic emissions due to the industrial area of Porto Marghera, the urban centres, and the glass factories and with emissions by ships traffic within the Lagoon. Furthermore, since 2005, the Lagoon has also been affected by the construction of the MOSE (Modulo Sperimentale Elettromeccanico—Electromechanical Experimental Module) mobile dams, as a barrier against the high tide. This work presents and discusses the results from chemical analyses of bulk depositions, carried out in different sites of the Venice Lagoon. Fluxes of pollutants were also statistically analysed on PCA with the aim of investigating the spatial variability of depositions and their correlation with precipitations. Fluxes of inorganic pollutants depend differently on precipitations, while organic compounds show a more seasonal trend. The statistical analysis showed that the site in the northern Lagoon has lower and almost homogeneous fluxes of pollutants, while the other sites registered more variable concentrations. The study also provided important information about the annual trend of pollutants and their evolution over a period of about five years, from 2005 to 2010

Organic micropollutants in wet and dry depositions in the Venice Lagoon

Atmospheric transport is an important route by which pollutants are conveyed from the continents to both coastal and open sea. The role of aerosol deposition in the transport of polycyclic aromatic hydrocarbons (PAHs), polychlorobiphenyls (PCBs) and polybromodiphenyls ethers (PBDEs) to water and soil systems has been evaluated by measuring their concentrations in wet and dry depositions to the Venice Lagoon. The organic micropollutant flux data indicate that they contribute to the total deposition flux in different ways through wet and dry deposition, showing that the prevalent contribution derives from wet deposition. The fluxes calculated for PBDEs, showed the prevalence of 47, 99, 100 and 183 congeners, both in dry and wet fluxes. With regard to PCBs, the flux of PPCB for wet deposition is in the same order of magnitude of the diffusive flux at the air–water interface. The PAH fluxes obtained in the present study are similar to those obtained in previous studies on the atmospheric bulk deposition to the Venice Lagoon. The ratios between Phe/Ant and Fl/Py indicate that the pollutants sources are pyrolytic, deriving from combustion fuels

Size distributed aerosol mass concentration and chemical composition in Belgrade during summer-autumn 2008

Physical and chemical characterizations of the atmospheric aerosol were carried out in urban area of Belgrade. This work focuses on the size-segregated aerosol chemical composition observed during the summer-autumn 2008th. Aerosol samples were submitted to gravimetric and chemical analyses. Mean random uncertainties associated with determination of Na+ , NH4 +, K+, Mg2+, Ca2+, Cl-, NO3- and SO42- were assessed

Trace elements in size-segregated urban aerosol in relation to the anthropogenic emission sources and the resuspension

Size segregated particulate samples of atmospheric aerosols in urban site of continental part of Balkans were collected during 6 months in 2008. Six stages impactor in the size ranges: Dp ≤ 0.49 μm, 0.49 < Dp ≤ 0.95 μm, 0.95 < Dp ≤ 1.5 μm, 1.5 < Dp ≤ 3.0 μm, 3.0 < Dp ≤ 7.2 μm, and 7.2 < Dp ≤ 10.0 μm was applied for sampling. ICP-MS was used to quantify elements: Al, As, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ga, K, Li, Na, Ni, Mg, Mn, Pb, Sb, V, and Zn. Two main groups of elements were investigated: (1) K, V, Ni, Zn, Pb, As, and Cd with high domination in nuclei mode indicating the combustion processes as a dominant sources and (2) Al, Fe, Ca, Mg, Na, Cr, Ga, Co, and Li in coarse mode indicating mechanical processes as their main origin. The strictly crustal origin is for Mg, Fe, Ca, and Co while for As, Cd, K, V, Ni, Cu, Pb, and Zn dominates the anthropogenic influence. The PCA analysis has shown that main contribution is of resuspension (PC1, σ2 ≈ 30 %) followed by traffic (PC2, σ2 ≈ 20 %) that are together contributing around 50 % of elements in the investigated urban aerosol. The EF model shows that major origin of Cd, K, V, Ni, Cu, Pb, Zn, and As in the fine mode is from the anthropogenic sources while increase of their contents in the coarse particles indicates their deposition from the atmosphere and soil contamination. This approach is useful for the assessment of the local resuspension influence on element’s contents in the aerosol and also for the evaluation of the historical pollution of soil caused by deposition of metals from the atmosphere

Comparison of PM10 concentrations and metal content in three different sites of the Venice Lagoon: An analysis of possible aerosol sources

The Venice Lagoon is exposed to atmospheric pollutants from industrial activities, thermoelectric power plants, petrochemical plants, incinerator, domestic heating, ship traffic, glass factories and vehicular emissions on the mainland. In 2005, construction began on the mobile dams (MOSE), one dam for each channel connecting the lagoon to the Adriatic Sea as a barrier against high tide. These construction works could represent an additional source of pollutants. PM10 samples were taken on random days between 2007 and 2010 at three different sites: Punta Sabbioni, Chioggia and Malamocco, located near the respective dam construction worksites. Chemical analyses of V, Cr, Fe, Co, Ni, Cu, Zn, As, Mo, Cd, Sb, Tl and Pb in PM10 samples were performed by Inductively coupled plasmaquadrupole mass spectrometry (ICP-QMS) and results were used to identify the main aerosol sources. The correlation of measured data with meteorology, and source apportionment, failed to highlight a contribution specifically associated to the emissions of the MOSE construction works. The comparison of the measurements at the three sites showed a substantial homogeneity of metal concentrations in the area. Source apportionment with principal component analysis (PCA) and positive matrix factorization (PMF) showed that a four principal factors model could describe the sources of metals in PM10. Three of them were assigned to specific sources in the area and one was characterised as a source of mixed origin (anthropogenic and crustal). A specific anthropogenic source of PM10 rich in Ni and Cr, active at the Chioggia site, was also identified

Protolysis studies and quantification of acids and bases in aqueous solutions by microelectrode voltammetry

Acid-base equilibria are generally studied and taught at universities using approaches and techniques that include the use of dyes, spectrophotometry, conductometry and potentiometry. Instead, voltammetric techniques, although employed for research purposes for acid-base investigations, have rarely been included in electrochemical curricula. In this article we highlight the potential of microelectrode voltammetry in studying acid-base equilibria, their kinetics and the acid and base content in aqueous solutions by exploiting the hydrogen and oxygen evolution reactions. Microelectrodes are used as they allow the attainment of reproducible and well-defined convergent mass-transport conditions and the achievement of steady-state diffusion regimes in short times. The resulting steady-state limiting current is proportional to bulk concentration, diffusion coefficient and electrode radius, which is useful for a more precise evaluation of each of latter quantities. Mention is also made on how mathematical treatments and digital simulation procedures can help in the classification and parameterization of the electrode processes involved

Trace Electroanalysis of Perfluorinated Alkyl Substances with Molecularly Imprinted Polymer Sensors

Pollution of natural and drinkable waters by perfluorinated alkyl substances (PFAS) is a problem of global concern [1]. [...

31st EFFoST International Conference 2017

Trace heavy metals dangerous to human health, as Pb, As or Cu, can be present in olive oil because of contamination from soil and fertilizers, production or storage procedures, or exposition of the olive plants to vehicular and industrial emissions. The analysis of metal ions in such highly viscous organic matrix by using conventional analytical procedures is rather challenging since it requires the application of series of strong and time-consuming pretreatment steps which can be a source of contamination of the sample, possibly reflecting in scarce accuracy and precision. In this work we present a novel analytical approach that combines electrochemical preconcentration with spectroscopic analysis, focusing on the determination of lead in olive oil as a case study. In order to perform electrochemical experiments in such a complex and low-conductive food matrix, the room temperature ionic liquid (RTIL) [P14,6,6,6]+[NTf2]-, which is soluble in vegetable oils, was used as supporting electrolyte. For the development and validation of the analytical approach, at first, standard solutions of lead in non-aqueous medium were produced by an electrochemical procedure based on the galvanostatic anodic dissolution of high-purity Pb in RTIL. The analytical strategy developed here for the assessment of Pb content in oils can be summarized in the following steps: 1) mixing of the oil with the RTIL; 2) potentiostatic electrochemical metal deposition onto a thin Pt coil, directly from the tested real sample, 2 mL volume; 2) potentiostatic anodic stripping of the metal deposit after transfer to aqueous acid solution; 3) spectroscopic (ICP-MS or GF-AAS) analysis of the solution collected. The feasibility and performance of this analytical protocol were tested both in standard solutions of Pb(II) in RTIL, and in oil samples mixed with RTIL 0.5 M and spiked with Pb. Particular attention was devoted to the optimization of the potentiostatic deposition and re-oxidation parameters, by resorting to an experimental design model properly set up to get optimal conditions in terms of efficiency of deposition/stripping steps, quantitative recovery and measurement time. The proposed procedure was finally applied to the determination of Pb content in some Italian extra virgin olive oils. From the results obtained, it can be concluded that the combination of this simple and fast electrochemical preconcentration/stripping protocol followed by spectroscopic analytical quantification is a promising analytical strategy for the assessment of trace metal contaminants in edible oils, avoiding mineralization or other time-consuming pretreatments of the complex food matrix