Blueberries as a Source of Energy: Physical Chemistry Characterization of Their Anthocyanins as Dye-Sensitized Solar Cells’ Sensitizers

This work aimed to show the possibility of applying anthocyanins extracted from blueberries following a straightforward path as potential impregnation dyes in dye-sensitized solar cells (DSSCs), particularly in the presence of co-adsorbents, such as silver nanoparticles, as an alternative in order to profit from large amounts of discarded fruits. Following a simple procedure, anthocyanins (mainly delphinidin-3-glucoside) were obtained from blueberries (Southern Highbush type). Complete characterization was carried out in order to prove the utility of delphinidin-3-glucoside as a sensitizer in DSSCs. The analyzed anthocyanin is suitable for sensitizing because of its high molar absorptivity values within the visible region of the light spectra, the adsorption ability to a FTO/TiO2 electrode (FTO, fluorine-doped tin oxide) as confirmed by Fourier transform infrared (FTIR) as well as thermogravimetry coupled to differential scanning calorimetry (TG-DSC), a potential oxidation value near 1 V, and adequate thermal as well as light stabilities. Moreover, the cell’s conversion efficiency is improved in the presence of silver nanoparticles, reaching 0.24% (nearly a 25% increase). The sum of all these characteristics points to the application of delphinidin-3-glucoside as a sensitizer in DSSCs, offering a technological use with potential interest for countries where agricultural production offers an abundant origin of extraction

Identification of microplastics in wastewater samples by means of polarized light optical microscopy

Many reports state the potential hazards of microplastics (MPs) and their implications to wildlife and human health. The presence of MP in the aquatic environment is related to several origins but particularly associated to their occurrence in wastewater effluents. The determination of MP in these complex samples is a challenge. Current analytical procedures for MP monitoring are based on separation and counting by visual observation or mediated with some type of microscopy with further identification by techniques such as Raman or Fourier-transform infrared (FTIR) spectroscopy. In this work, a simple alternative for the separation, counting and identification of MP in wastewater samples is reported. The presented sample preparation technique with further polarized light optical microscopy (PLOM) observation positively identified the vast majority of MP particles occurring in wastewater samples of Montevideo, Uruguay, in the 70–600 μm range. MPs with different shapes and chemical composition were identified by PLOM and confirmed by confocal Raman microscopy. Rapid identification of polyethylene (PE), polypropylene (PP) and polyethylene terephthalate (PET) were evidenced. A major limitation was found in the identification of MP from non-birefringent polymers such as PVC (polyvinylchloride). The proposed procedure for MP analysis in wastewater is easy to be implemented at any analytical laboratory. A pilot monitoring of Montevideo WWTP effluents was carried out over 3-month period identifying MP from different chemical identities in the range 5.3–8.2 × 10 MP items/m.With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737

Validation and application of a methodology based in ionic Cromatography with UV detection for nitrate and nitrite determination in waters of the Rio de la Plata

La determinación por cromatografía iónica con detector de conductividad (CI-DC) de elementos trazas como el nitrato y nitrito, ya sea en modos de supresión o sin supresión, ha mostrado ser muy útil en diferentes matrices. Sin embargo, en matrices ambientales con alta concentración de haluros como aguas marinas o estuarinas, la determinación de estos analitos necesita de estrategias más eficientes para la remoción de interferencias. Por tal motivo, se ha buscado una alternativa de determinación de nitrato y nitrito en estas matrices empleando sistemas de detección más selectivos que el CDD tales como el detector UV y la utilización de extracción en fase solida (SPE) con cartuchos comerciales IC-Ag (Alltech Inc., EE.UU) para la remoción de interferencias. En este trabajo, se presenta la validación de una metodología de determinación de nitrato y nitrito por cromatografía iónica con detector UV (210 nm) en muestras de aguas superficiales de playas de la ciudad de Montevideo, Uruguay. Se identificó un valor de salinidad máximo de estas aguas para la determinación de estos analitos de manera directa, evitando el tratamiento por SPE para remoción de cloruros. El procedimiento analítico fue validado para las siguientes cifras de mérito: linealidad, intervalo de trabajo, efecto matriz, repetitividad, límite de detección, límite de cuantificación, precisión intermedia, robustez e incertidumbre definidas según el Organismo Uruguayo de Acreditación. Se destaca la robustez de la metodología, medida a través de un diseño estadístico factorial, con límites de detección para nitrato de 0.02 mg/L y 0.01 mg/L para nitrito y precisión intermedia medida como desviación estándar relativa (tres operadores en semanas diferentes) para muestras reales de 4.7 %. Se presentan además, resultados del monitoreo llevado a cabo en campañas durante el invierno y verano de los años 2011 y 2012, respectivamente, para estos analitos, dado su interés para determinar el nivel de eutrofización de las aguas de Montevideo.The determination of trace elements such as nitrate and nitrite by ion chromatography with a conductivity detector (CI-CD), with or without ionic suppression modes, has proved to be very useful for different matrices. However, in environmental matrices with high concentrations of halides such as marine or brine waters, the determination of these analytes requires more efficient strategies for the removal of interferences. In this work, we have searched for a rugged alternative in the determination of nitrate and nitrite in these matrices using solid phase extraction (SPE) with IC-Ag (Alltech Inc., USA) commercial cartridges for the removal of interferences and UV absorption detection. We present method validation data in the determination of nitrate and nitrite in surface waters from beaches of Montevideo, Uruguay by ion chromatography with UV detection (210 nm). For these samples, it was identified a cut-off value of salinity to directly determine these analytes, avoiding the SPE treatment for the removal of chloride. The analytical procedure was validated for the following figures of merit: linearity, dynamic range, matrix effect (interferences study), repeatability, limit of detection, limit of quantitation, intermediate precision, robustness and uncertainty defined by the Organismo Uruguayo de Acreditación. The robustness of this methodology, measured through a factorial statistical design is satisfactory while detection limits for nitrate is 0.02 mg / L and 0.01 mg / L for nitrite. Intermediate precision measured as relative standard deviation (three operators in different weeks) for real samples showed to be 4.7 %. We also depict results of a winter to summer monitoring campaign (2011 to 2012 season) for these analytes, taking into account the importance of determining the eutrophication level in Montevideo certified beaches.Asociación de Universidades Grupo Montevide