CeO2 nanostructured electrochemical sensor for the simultaneous recognition of diethylstilbestrol and 17ß-estradiol hormones.

A new highly sensitive, selective, and inexpensive electrochemical method has been developed for simultaneously detecting diethylstilbestrol (DES) and 17ß-estradiol (E2) in environmental samples (groundwater and lake water) using a graphite sensor modified by cerium oxide nanoparticles (CPE-CeO2 NPs). The developed sensor and the materials used in its preparation were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The ab initio simulation was used to evaluate the adsorption energies between both DES and E2 with the surface of the sensor. The peak current of oxidation of both hormones showed two regions of linearity. The region of greatest sensitivity was observed for the linear range of 10 nM-100 nM. The detection and quantification limits for this concentration range were 0.8/2.6 nM and 1.3/4.3 nM for DES and E2, respectively. The analytical performance of the developed method showed high sensitivity, precision, repeatability, reproducibility, and selectivity. The CPE-CeO2 NPs sensor was successfully applied to simultaneously detect DES and E2 in real samples with recovery levels above 98%.

An efficient and simple method using a graphite oxide electrochemical sensor for the determination of glyphosate in environmental samples.

Excessive and indiscriminate use of the herbicide glyphosate (GLY) leaves the environment susceptible to its contamination. This work describes the development of a simple, inexpensive, and efficient electroanalytical method using graphite oxide paste electrode (GrO-PE) for the direct determination of GLY traces in groundwater samples, soybean extracts, and lettuce extracts. Under optimal experimental conditions, the developed sensor exhibited a linear response of the peak current intensity vs. the concentration, in the range of 1.8 × 10-5 to 1.2 × 10-3 mol L-1 for GLY. The limits of detection and quantification are 1.7 × 10-8 mol L-1 and 5.6 × 10-8 mol L-1, respectively. The methodology developed here demonstrated a strong analytical performance, with high reproducibility, repeatability, and precision. Moreover, it successfully avoided interference from other substances, showing high selectivity. The GrO-PE sensor was effectively applied to determine GLY traces in real samples with recovery rates ranging from 98% to 102%. Results showed that the GrO-PE is effective and useful for GLY detection, with the advantage of not involving laborious modifications and complicated handling, making it a promising tool for environmental analysis.

In vitro and in vivo impact assessment of eco-designed CuO nanoparticles on non-target aquatic photoautotrophic organisms.

This work has assessed the impact of copper oxide nanoparticles (CuONPs), designed via green route, toward photosynthetic apparatus on aquatic photoautotrophic organisms. In order to filling knowledge gaps, in vitro and in vivo assays were performed, using cyanobacterial phycocyanin (C-PC) from Arthrospira platensis and Lemna valdiviana plants (duckweed), respectively. Impairment in light energy transfer became evident in C-PC exposed to CuONPs, giving rise to an increase of light absorption and a suppression of fluorescence emission. Fourier transform infrared spectroscopy (FTIR) results showed that C-PC structures might be altered by the nanoparticles, also revealed that CuONPs preferably interacts with -NH functional groups. The data also revealed that CuONPs affected the chlorophyll a content in duckweed leaves. In addition, photosystem II (PSII) performance was significantly affected by CuONPs, negatively impacting the PSII photochemical network. In summary, the results point out that, even eco-friendly designed, CuONPs may negatively affect the photosynthetic process when accumulated by aquatic photoautotrophs.

Degradation of metformin in water by TiO2-ZrO2 photocatalysis.

The increasing use of pharmaceutical products also increases their release in aquatic environment. These contaminants are considered emerging pollutants, and induce adverse ecological and human health effects. The antidiabetic metformin is one example that has been detected in the aquatic environment at unusual concentrations. This fact indicates that conventional wastewater treatment is inefficient on eliminating this compound. Here we show that metformin can be effectively removed from water by photocatalysis. We found the optimised conditions for pH and concentration of catalyst on the photocatalytic process. TiO2 and TiO2-ZrO2 were successful in oxidising metformin under UV radiation following a pseudo-first order kinetics. Intermediates of metformin photodegradation appeared after photocatalytic treatment. Toxicity analysis showed that the degradation products are non-toxic to Lactuca sativa seeds.

A new simple electrochemical method for the determination of Bisphenol A using bentonite as modifier.

A simple, inexpensive, highly sensitive, selective, and novel electrochemical method was developed for determination of the Bisphenol A in samples of tap water, blood serum, and urine using a bentonite-modified carbon paste electrode. The graphite, bentonite and the working electrodes (without and chemically modified) were characterized by scanning electron microscopy, infrared absorption spectroscopy, and X-ray diffraction. The electrodes were electrochemically characterized using cyclic voltammetry, square wave voltammetry, and electrochemical impedance spectroscopy. The studied electrochemical variables were: electrode area, standard heterogeneous rate constant, charge transfer coefficient and double-layer capacitance. The bentonite as a sensor modifier had a strong influence on these variables. For the development of the methodology to quantify Bisphenol A, the instrumental parameters (frequency, amplitude, and step potential) and experimental parameters (pH, bentonite quantity) were optimized. The analytical curve to Bisphenol showed a linear response of the oxidation peak current intensity vs. the concentration in the range of 6.8 × 10-10 to 1.5 × 10-8 mol mL-1, with a limit of detection (LOD) of 2.11 × 10-11 mol mL-1 and limit of quantification (LOQ) of 7.04 × 10-11 mol mL-1. Recovery experiments were performed by adding known amounts of Bisphenol A in tap water, blood serum, and urine samples. Recovery rates using the standard addition method were in the range of 97.8-101.8%. The results demonstrated the method feasibility for quantifying Bisphenol A in these samples.