Phosphorus is an element that is difficult to determine accurately by most analytical techniques. In particular, phosphorus determination by means of electrothermal atomic absorption spectrometry (ETAAS) has been traditionally hampered by (i) the practical inability of using phosphorus resonance lines; (ii) its complex chemical behaviour (e.g., formation of volatile compounds and a tendency to interact with graphite); and, particularly, (iii) the overlap observed between molecular and atomic phosphorus lines, which makes it very difficult to obtain reliable results when using line source-ETAAS. In this work, the potential of high resolution-continuum source ET spectrometry for the direct determination of phosphorus in biological solid samples is demonstrated. Two different methodologies, based on the monitoring of either atomic or molecular lines, were compared, paying special attention to the judicious selection of the chemical modifier and the temperature program that will be most adequate to the intended purpose. In order to enable atomic phosphorus monitoring, a high atomization temperature (2650 °C) and a combination of chemical modifiers consisting of palladium, ascorbic acid and tungsten (as permanent modifier) were used. On the other hand, when monitoring PO lines, tungsten coating and vaporization at only 1900 °C proved to be sufficient for attaining reliable results, although attention has to be paid to the possible effect of spectral interferences (e.g., NO lines). Both methods permitted the direct analysis of the samples under investigation, offering a high sample throughput (about 15–20 minutes per determination), good sensitivity (m₀ around 5 ng and LODs at the µg g⁻¹ level), RSD values in the 5–10% range, and straightforward calibration with aqueous standards.

The Tungurahua volcano, located in the eastern mountain range of Ecuador, since its reactivation in 1999 has had several phases of volcanic activity, which have produced gas, ash and lava emissions. These emissions release a large amount of metals to nearby soils that are currently used for agricultural purposes. Metal pollution can cause serious problems for human health; while other metals are necessary as nutrients in most agricultural crops. In this investigation, the metal content in agricultural soils of the Quero canton was evaluated, as well as its bioavailability and content in the culture of Allium fistulosum L., in order to obtain information on the impact of potentially polluting metals (cadmium, lead, nickel, strontium, cobalt, copper and zinc) and nutrients (potassium, magnesium, iron and manganese) on crops. For the estimation of total metals in soil an acid digestion was performed; for bioavailable metals an extractant mixture (EDTA-Triethanolamine-CaCl2, pH 7) was used and for the branch onion a calcination followed by acid digestion was carried out. The quantification of the metals was carried out by flame atomic absorption spectroscopy or graphite furnace. The results showed that the metal content, both in the soil samples and in the branch onion, was below the maximum values allowed in the local regulations for all the metals studied. In addition,the intake of the metal by the branch onion was independent of the bioavailable fraction.

Surface-plasmon-based biosensors have become excellent platforms for detecting biomolecular interactions. While there are several methods to exciting surface plasmons, the major challenge is improving their sensitivity. In relation to this, graphene-based nanomaterials have been theoretically and experimentally proven to increase the sensitivity of surface plasmons. Notably, graphene nanoribbons display more versatile electronic and optical properties due to their controllable bandgaps in comparison to those of zero-gap graphene. In this work, we use a semi-analytical approach to investigate the plasmonic character of two-dimensional graphene nanoribbon arrays, considering free-standing models, i.e., models in which contact with the supporting substrate does not affect their electronic properties. Our findings provide evidence that the plasmon frequency and plasmon dispersion are highly sensitive to geometrical factors or the experimental setup within the terahertz regime. More importantly, possible applications in the molecular detection of lactose, α-thrombin, chlorpyrifos-methyl, glucose, and malaria are discussed. These predictions can be used in future experiments, which, according to what is reported here, can be correctly fitted to the input parameters of possible biosensors based on graphene nanoribbon arrays.

El morete (Mauritia fleuxosa L. f.) es una palmera de la Amazonía que produce un fruto de agradable sabor, buen valor nutricional y alto contenido de aceite. El objetivo de la presente investigación fue estudiar el efecto del tratamiento térmico de las diferentes partes del morete en el rendimiento y perfil de ácidos grasos del aceite obtenido por prensado. Se aplicó un diseño de bloques completos al azar con tres réplicas, combinando el uso de pulpa y pulpa con corteza del fruto en diferentes condiciones de calentamiento antes del prensado: 45 °C por 30 min, 65 °C por 20 min y 85 °C por 10 min. También, se determinó la estabilidad oxidativa del aceite empleando un Reactor Oxitest. Se obtuvieron aceites con diferentes contenidos de ácidos grasos saturados, monoinsaturados y poliinsaturados, prevaleciendo el ácido oleico. El mejor tratamiento fue empleando la pulpa calentada a 85 °C por 10 min y prensada, encontrándose un rendimiento de 56,77% de aceite con 79,80% de ácido oleico, y una estabilidad a la oxidación de 14,5 meses a 21 °C, temperatura promedio de la ciudad de El Puyo, Ecuador, sitio donde se recolectó el morete. Por otro lado, se debe evaluar el efecto de esta temperatura previa a la extracción sobre el contenido de compuestos bioactivos y la posibilidad de oxidación de las grasas. En conclusión, el morete es una fuente de aceite y la tecnología de tratamiento con calor permitirá mejorar la extracción e industrialización, y ofrecer un aceite alternativo para la alimentación.

Cold-pressed chia oil (Salvia hispanica L.) is highly susceptible to oxidative deterioration due to its exceptional α-linolenic acid content. This study evaluated the effect of increasing α-tocopherol concentrations (0–0.10% w/w) on its oxidative stability through accelerated oxidation testing (Oxitest) and long-term refrigerated storage. α-Tocopherol was selected because it is a widely accepted antioxidant in edible oils according to the Codex Alimentarius and FAO/WHO guidelines. A randomized block design (n = 3 independent extraction batches) was used to determine the induction period (IP) at 80 °C, followed by a 15-month evaluation at 15 °C of the control and the most promising treatment. α-Tocopherol increased oxidative resistance in a dose-dependent manner, but concentrations above 0.05% offered no additional benefits. The 0.05% treatment significantly prolonged the IP and effectively limited increases in peroxide and acidity values, keeping all parameters within Ecuadorian regulatory limits and consistent with international quality standards. Fatty-acid profiling confirmed that this antioxidant level slowed α-linolenic acid degradation, preserving the PUFA-rich profile of chia oil. These findings show that low-level α-tocopherol supplementation is a practical strategy to improve long-term stability of cold-pressed chia oil without altering its nutritional properties, providing valuable evidence for the formulation and commercialization of premium functional oils.

Los ecosistemas costeros reciben impactos negativos por actividades industriales, explotación de especies costeras, actividades turísticas y recreativas, lo que hace necesario evaluar su calidad ambiental. El objetivo de este trabajo fue estudiar la variabilidad de las actividades enzimáticas de catalasa, ureasa y proteasa en suelos arenosos de playas del municipio Puerto Cabello, estado Carabobo para su uso como indicadores de calidad ambiental. Las playas estudiadas fueron El Palito (EP), Waikiki (W) y Playa Blanca (PB). Se establecieron cuatro unidades de muestreo: zona lejana (L), zona cercana (C), zona seca (S), zona húmeda (H), tomando muestras superficiales (s) y sub-superficiales (ss) en época lluviosa y seca. Se determinaron parámetros fisicoquímicos y las actividades enzimáticas de catalasa, ureasa y proteasa. La actividad de catalasa, muestra variabilidad asociada a las zonas evaluadas, pero no se evidencian variaciones estacionales. La actividad de ureasa, refleja una variabilidad con respecto a las zonas de la playa y la fuente contaminante; mientras que la actividad proteasa no muestra variación estacional, pero si respecto a las zonas de la playa y la fuente contaminante. Se evidenció una correlación negativa significativa entre la actividad catalasa y el contenido de arena, retención de humedad, materia orgánica y una correlación positiva entre la actividad de la ureasa y el contenido de materia orgánica. Finalmente, se concluye que las actividades enzimáticas de catalasa, ureasa y proteasa son sensibles ante impactos antropogénicos, por lo que pueden ser usadas como indicadores de calidad en los suelos arenosos evaluados. Palabras clave: Catalasa; indicadores de calidad de suelo; proteasa; suelos arenosos; ureasa.