A portable setup for the voltammetric determination of total mercury in fish with solid and nanostructured gold electrodes

A simple procedure for field fish sample pretreatment was developed. This treatment in combination with square wave anodic stripping voltammetry (SW-ASV) with solid gold electrodes (SGE) and gold nanoparticle-modified glassy carbon electrodes (AuNPs-GCE) was applied for the determination of total mercury content. A certified reference material (CRM, Tuna Fish BCR 463), ten freeze-dried samples of canned tuna and two fresh fish samples were analysed both with a bench-top voltammetric analyser after microwave digestion and with a portable potentiostat after mild eating using a small commercial food warmer. The results obtained by the two SW-ASV approaches and by a Direct Mercury Analyser (DMA), the official method for mercury determination, were in very good agreement. In particular, (i) the results obtained with in field procedure are consistent with those obtained with the conventional microwave digestion; (ii) the presence of gold nanoparticles on the active electrode surface permits an improvement of the analytical performance in comparison to the SGE: the Limit of Quantification (LOQ) for mercury in fish-matrix was 0.1 μg L−1 (Hg cell concentration), corresponding to 0.06 mg kg−1 wet fish, which is a performance comparable to that of DMA. The pretreatment proposed in this study is very easy and applicable to fresh fish; in combination with a portable potentiostat, it proved to be an interesting procedure for on-site mercury determination

Accumulation of As, Cd, Pb, and Zn in sediment, chironomids and fish from a high-mountain lake: First insights from the Carnic Alps

Though mountain lakes are generally much less influenced by human activities than other habitats, anthropogenic threats can still alter their natural condition. Amajor source of global environmental pollution inmountain ecosystems is trace element contamination. For this studywe investigated for the first time the accumulation of As, Cd, Pb, and Zn in sediment, Diptera Chironomidae (prey), and bullhead Cottus gobio (predator) in a typical high-mountain lake (Dimon Lake) in the Carnic Alps. Significant differences in trace element levels were observed between sediment, Diptera Chironomidae, and C. gobio liver and muscle samples (Kruskal-Wallis test; p b .03 for all elements). As and Pb levels were highest in sediment, Cd and Zn levels were highest in Diptera Chironomidae, and the lowest values for all elementswere measured in C. gobio muscle and liver. Bioaccumulation factor values weremuch higher in Diptera Chironomidae than fish muscle and liver, with the highest values recorded for Cd (5.16) and Zn (4.37). Trophic transfer factor valueswere very lowfor all elements in fish muscle and liver, suggesting a biodilution effect along the food chain. Further studies are needed to expand on these first findings that provide useful insights to inform environmental monitoring and policy in remote high-mountain lakes

Identification of Illicit Conservation Treatments in Fresh Fish by Micro-Raman Spectroscopy and Chemometric Methods

In the field of food control for fresh products, the identification of foods subjected to illicit conservation treatments to extend their shelf life is fundamental. Fresh fish products are particularly subjected to this type of fraud due to their high commercial value and the fact that they often have to be transported over a long distance, keeping their organoleptic characteristics unaltered. Treatments of this type involve, e.g., the bleaching of the meat and/or the momentary abatement of the microbial load, while the degradation process continues. It is therefore important to find rapid methods that allow the identification of illicit treatments. The study presented here was performed on 24 sea bass samples divided into four groups: 12 controls (stored on ice in the fridge for 3 or 24 h), and 12 treated with a Cafodos-like solution for 3 or 24 h. Muscle and skin samples were then characterized using micro-Raman spectroscopy. The data were pre-processed by smoothing and taking the first derivative and then PLS-DA models were built to identify short- and long- term effects on the fish's muscle and skin. All the models provided the perfect classification of the samples both in fitting and cross-validation and an analysis of the bands responsible for the effects was also reported. To the best of the authors' knowledge, this is the first time Raman spectroscopy has been applied for the identification of a Cafodos-like illicit treatment, focusing on both fish muscle and skin evaluation. The procedure could pave the way for a future application directly on the market through the use of a portable device