Seafood consumption is the primary exposure route for trace metals like mercury. Accordingly, canned tuna meat has been focused on by researchers because of the potential bioaccumulation of high amounts of mercury. This study aimed to test a novel and reliable electroanalytical method employing a working electrode consisting of gold-nanoparticle-modified carbon microfibers to quantify total mercury in canned tuna samples. Determination was achieved via differential pulse anodic stripping voltammetry. The proposed method had a limit of detection of 3.9781 ± 0.0001 μg L^-1 and a limit of quantification of 33.6634 ± 0.0001 μg L^-1, with a sensitivity of 0.3275 nA μg L^-1. The modified electrode was evaluated in samples taken from three canned tuna brands sold in the Sangolquí parish in Rumiñahui, Ecuador. These brands, coded A, B, and C, represent 47.92%, 27.08%, and 11.98% of all canned tuna sold in the Ecuadorian market, respectively. The resulting respective total mercury concentrations were 0.5999 ± 0.0001 mg kg^-1; 0.9387 ± 0.0001 mg kg^-1; and 0.3442 ± 0.0001 mg kg^-1 for A, B, and C. Method accuracy was determined through the recovery percentages of ≥98%, which indicated acceptable accuracy for the final optimized method. Mean mercury concentrations for all samples did not represent a carcinogenic risk for consumers. However, the values obtained for potential no-carcinogenic risk and daily consumption rate suggest that consumers of tuna canned in water, particularly brand C, may be at risk.

This work reports on the assessment of a non-hydrolytic electrochemical sensor for glucose sensing that is developed using functionalized carbon nanotubes (fCNTs)/Co(OH)₂. The morphology of the nanocomposite was investigated by scanning electron microscopy, which revealed that the CNTs interacted with Co(OH)₂. This content formed a nanocomposite that improved the electrochemical characterizations of the electrode, including the electrochemical active surface area and capacitance, thus improving sensitivity to glucose. In the electrochemical characterization by cyclic voltammetry and chronoamperometry, the increase in catalytic activity by Co(OH)₂ improved the stability and reproducibility of the glucose sensor without the use of enzymes, and its concentration range was between 50 and 700 μmol L⁻¹. The sensor exhibited good linearity towards glucose with LOD value of 43.200 µmol L⁻¹, which proved that the Co(OH)₂-fCNTs composite is judicious for constructing cost effective and feasible sensor for glucose detection.

The native berries of South America present promising marketing opportunities owing to their high antioxidant content, notably rich in anthocyanin and phenolic compounds. However, Ecuador's endemic fruits, primarily found in the wild, lack comprehensive data regarding their phytochemical composition and antioxidant capacity, underscoring the need for research in this area. Accordingly, this study evaluated the total phenolic, anthocyanin, flavonoid, resveratrol, ascorbic acid, citric acid, sugars, and antioxidant content of three native Ecuadorian fruits: mora de monte (Rubus glabratus Kunth), mortiño (Vaccinium floribundum Kunth), and tuna de monte (Opuntia soederstromiana). Determination of resveratrol, ascorbic acid, citric acid, and sugars was determined by HPLC analysis, and UPLC analysis was used to determine tentative metabolites with nutraceutical properties. Antioxidant capacity was assessed using cyclic voltammetry and the DPPH method; differential pulse voltammetry was used to evaluate antioxidant power. Analysis of results through UPLC-QTOF mass spectrometry indicated that R. glabratus Kunth and V. floribundum Kunth are important sources of various compounds with potential health-promoting functions in the body. The DPPH results showed the following antioxidant capacities for the three fruits: R. glabratus Kunth > O. soederstromiana > V. floribundum Kunth; this trend was consistent with the antioxidant capacity results determined using the electrochemical methods.

El mercurio es considerado un contaminante altamente peligroso debido a su elevada toxicidad y a su carácter acumulativo. Presenta varios efectos en la salud humana tales como: trastornos del sistema nervioso, deterioro intelectual, problemas gastrointestinales y cáncer. El uso de técnicas electroquímicas es una alternativa para la cuantificación de mercurio a niveles traza, debido a su bajo costo y buena sensibilidad. En este trabajo de investigación se evaluó un microelectrodo de fibra de carbono modificado con nanopartículas de oro para la determinación de mercurio (II) en medio acuoso. Se realizó la modificación superficial de la fibra de carbono electrodepositando nanopartículas de oro, a un potencial de -0,1 V durante 100 s, y se utilizó microscopía electrónica de barrido y voltamperometría cíclica para confirmar la presencia de nanopartículas de oro. Se cuantificó el mercurio (II) mediante voltamperometría de redisolución anódica de pulso diferencial. Se obtuvo un rango lineal, en la curva de calibración, entre 50 - 100 µg L^-1 de mercurio (II). Los límites de detección y de cuantificación obtenidos fueron de 38 y 46 µg L^-1, respectivamente. La validación de la metodología se realizó mediante porcentaje de recuperación, obteniendo valores entre 94 y 104 % y desviación estándar relativa (RSD, por sus siglas en inglés) entre 3,6 y 4,7 %. El método propuesto muestra características útiles para su implementación en el monitoreo de contaminación por mercurio.