This work focuses on the sustainable green synthesis of magnetic iron oxide nanoparticles (Fe₃O₄NPs) using bioreductants derived from orange peel extracts for application in the efficient oxygen evolution reactions (OER). The synthesized catalysts were characterized using X-ray diffraction analysis, field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDS), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and UV–visible spectroscopy. The Fe₃O₄NPs exhibit a well-defined spherical morphology with a larger Brunauer–Emmett–Teller surface area and a significant electrochemically active surface area. The green synthesis using orange peel extracts leads to an excellent electrocatalytic activity of the apparent spherical Fe₃O₄NPs (diameter of 9.62 ± 0.07 nm), which is explored for OER in an alkaline medium (1.0 M KOH) using linear-sweep and cyclic voltammetry techniques. These nanoparticles achieved a benchmark current density of 10 mA cm⁻² at a low overpotential of 0.3 V versus RHE, along with notable durability and stability. The outstanding OER electrocatalytic activity is attributed to their unique morphology, which offers large surface area and an ideal porous structure that enhances the adsorption and activation of reactive species. Furthermore, structural defects within the nanoparticles facilitate efficient electron transfer and migration of these species, further accelerating the OER process.

The analytical surveillance of sulfite species (SO₃²⁻, SO₂ and HSO₃⁻) is critical for food safety due to their roles as preservatives and potent allergens. Despite stringent regulations, conventional methods like Monier-Williams distillation remain limited by labor-intensive protocols and matrix interferences. This review elucidates the chemical mechanisms of sulfites in food matrices and critically evaluates recent advancements in electrochemical sensing. A primary focus is placed on delineating physicochemical bottlenecks, such as electrode fouling and cross-reactivity from polyphenols and organic acids, which hinder commercialization. We analyze the strategic integration of nanostructured interfaces—including bimetallic nanoparticles, carbon-based hybrids (rGO/PPy), and nanozymes—to reduce oxidation overpotentials and enhance sensitivity below regulatory thresholds. Furthermore, the transition from laboratory prototypes to decentralized, field-deployable platforms using screen-printed electrodes (SPEs) and smartphone-based potentiostats is explored. By synthesizing technical innovations with “green” analytical principles, this work provides a roadmap for real-time quality control in the food industry, bridging the gap between fundamental electrochemistry and industrial scalability.

In some valleys in northern Chile, the natural water reservoirs used for human consumption contain high levels of boron (> 25 mg/L). In local Pre-Colombian populations, this resulted in overexposure which is harmful to human health, causing gastrointestinal and other issues. Boron levels vary regionally, with the Lluta and Camarones Valleys presenting higher mean values (14 and 25 mg/L, respectively) than the Azapa Valley (1 mg/L). To estimate concentrations in northern Chile’s pre-Columbian populations, we used molecular absorption spectrophotometry to analyze rib samples of 211 individuals from these valleys. All the ancient rib samples presented mean boron values approximately 7 to 23 times higher than the 10.2 mg/Kg reported for modern bone tissue. Levels were highest in inhabitants of the Lluta Valley (235.52 mg/Kg) and Camarones Valley (119.09 mg/Kg), followed by those from the Azapa Valley (69.97 mg/Kg). We conclude that boron overexposure significantly impacted northern Chile’s ancient populations, and the discussions of pre-Columbian settlements and biocultural trajectories should consider water quality.