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This work describes a study of the underpotential deposition (UPD) of Sn2+ on a polycrystalline gold disc electrode using cyclic voltammetry (CV) and chronocoulometry (CC). Sn2+ ions showed well-defined peaks from UPD and UPD stripping (UPD-S) in 1 mol/L HCl solutions, while bulk deposition (BD) and BD stripping (BD-S) of the ions were also observed. The measured UPD shifts, ΔEUPD, between the UPD-S and the BD-S peaks were more than 200 mV. The UPD charge and the surface coverage of tin were measured by CC. A new method for determining Sn2+ was therefore developed, based on the excellent electrochemical properties of the Au/Sn UPD system. A plot of the UPD-DPASV (differential pulse anodic stripping voltammetry) signal versus the Sn(II) concentration was obtained for [Sn(II)] of 1.98×10−7 to 3.64×10−5 M. The method developed here has been applied to determine the tin in a tin plate sample.

A new easy, sensitive and accurate AAS method using an inner miniature cup in conjunction with a cupped type electrothermal graphite furnace for the solid sampling technique is proposed for the determination of sub-ppb levels of Cd, Cu, Mn, Pb and Zn in lake or sea water. It implies direct measurement of the coprecipitate obtained by using a combination of dimethylglyoxime (DMG) and nickel ion as carrier element an 1-(2-pyridylazo)-2-naphthol (PAN) as an auxiliary complexing agent. Fundamental studies on the coprecipitation with the DMG/Ni/PAN complex have been carried out to determine sub-ppb levels of elements in water samples. The analytical sensitivity compared with a conventional method using GF-AAS was increased at least 1,000-fold, because the measurement of the coprecipitates was without redissolution. The standard deviations for 0.1–0.5 ppb Mn in water samples were found to be 1–5%.

A voltammetric biosensor for Ara h 6 (a peanut allergen) detection in food samples was developed. Gold nanoparticle-modified screen-printed carbon electrodes were used to develop a sandwich-type immunoassay using two-monoclonal antibodies. The antibody-antigen interaction was detected through the electrochemical detection of enzymatically deposited silver. The immunosensor presented a linear range between 1 and 100 ng/ml, as well as high precision (inter-day RSD ≤9.8 %) and accuracy (recoveries ≥96.7 %). The detection and quantification limits were 0.27 and 0.88 ng/ml, respectively. It was possible to detect small levels of Ara h 6 in complex food matrices.