Assessing the Fate of Superparamagnetic Iron Oxide Nanoparticles Carrying Usnic Acid as Chemical Cargo on the Soil Microbial Community.

In the present study we evaluate the effect of superparamagnetic iron oxide nanoparticles (SPIONs) carrying usnic acid (UA) as chemical cargo on the soil microbial community in a dystrophic red latosol (oxysol). Herein, 500 ppm UA or SPIONs-framework carrying UA were diluted in sterile ultrapure deionized water and applied by hand sprayer on the top of the soil. The experiment was conducted in a growth chamber at 25 °C, with a relative humidity of 80% and a 16 h/8 h light-dark cycle (600 lx light intensity) for 30 days. Sterile ultrapure deionized water was used as the negative control; uncapped and oleic acid (OA) capped SPIONs were also tested to assess their potential effects. Magnetic nanostructures were synthesized by a coprecipitation method and characterized by scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), zeta potential, hydrodynamic diameter, magnetic measurements, and release kinetics of chemical cargo. Uncapped and OA-capped SPIONs did not significantly affect soil microbial community. Our results showed an impairment in the soil microbial community exposed to free UA, leading to a general decrease in negative effects on soil-based parameters when bioactive was loaded into the nanoscale magnetic carrier. Besides, compared to control, the free UA caused a significant decrease in microbial biomass C (39%), on the activity of acid protease (59%), and acid phosphatase (23%) enzymes, respectively. Free UA also reduced eukaryotic 18S rRNA gene abundance, suggesting a major impact on fungi. Our findings indicate that SPIONs as bioherbicide nanocarriers can reduce the negative impacts on soil. Therefore, nanoenabled biocides may improve agricultural productivity, which is important for food security due to the need of increasing food production.

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.

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.

Direct electrochemical detection of glyphosate at carbon paste electrode and its determination in samples of milk, orange juice, and agricultural formulation.

This paper describes a simple, inexpensive, highly sensitive, selective, and efficient electrochemical method to determine glyphosate (GLY) in samples of milk, orange juice, and agricultural formulation. The oxidation reaction on the electrode surface was electrochemically characterised by cyclic voltammetry (CV) and square wave voltammetry (SWV). The investigation of GLY at carbon paste electrode revealed a non-reversible oxidation peak at +0.95 V versus Ag/AgCl, which was used for electrochemical detection of GLY. The operating parameters (pH, frequency, step potential, and amplitude) were optimised in relation to the peak current intensity, and a calibration curve was set up in a concentration range of 4.40 × 10-8-2.80 × 10-6 mol L-1, with a detection limit of 2 × 10-9 mol L-1. After calibration curve was plotted, the developed procedure was applied to determine GLY in previously contaminated samples: milk and orange juice, and in a commercial formulation, obtaining recovery values between 98.31% and 103.75%. These results show that the proposed method can be used for GLY quantification in different samples with high sensitivity, specificity, stability, and reproducibility.

Voltammetric detection of trifluralin in tap water, fruit juice, and vegetable extracts in the presence of surfactants.

This study describes a novel electrochemical method to determine the herbicide trifluralin in samples of water, fruit juice, and vegetable extracts in the presence of surfactants, using a glassy carbon electrode (GCE). In acidic media, trifluralin was irreversible on the glassy carbon electrode surface at -0.5 V vs. Ag/AgCl. Surfactant presence on the electrode-solution interface modified current intensities and shifted the reduction peak potential of trifluralin. Different types of surfactant and their concentrations were investigated. The anionic surfactant significantly enhanced the peak current intensity of trifluralin. Under optimal analytical conditions, an analytical curve was obtained in the concentration range of 0.48-32.20 µM. The limits of detection and quantification were estimated at 0.031 and 0.104 µM, respectively. The method was successfully applied to quantify trifluralin in samples of water, orange and tomato juice, and green pepper, carrot, and onion extracts, with recovery rates of 97.9-102.1%. The results were in good agreement with those obtained using high-performance liquid chromatography, indicating that the proposed electrochemical method can be employed to quantify trifluralin in various types foods, with sensitivity, specificity, selectivity and reproducibility.

Ultrasensitive determination of carbendazim in water and orange juice using a carbon paste electrode.

A carbon paste electrode was used for the electrochemical quantification of carbendazim in water and orange juice samples. Carbendazim oxidation on the electrode surface was found to be controlled by adsorption. The novel electrochemical procedure for carbendazim quantification employed differential pulse voltammetry using a carbon paste electrode under optimal conditions. Carbendazim oxidation currents were linear at concentrations of 2.84 to 45.44 µg L(-1), with a limit of detection of 0.96 µg L(-1). The proposed method was applied to carbendazim quantification in ultrapurified water, river water, and orange juice. Recovery rates in water and orange juice samples were in the 97%-101% range, indicating that the method can be employed to determine carbendazim in these matrices, with advantages including shorter analysis time and lower cost than routine methods such as chromatography or spectroscopy. The electrode showed good reproducibility, remarkable stability, and especially good surface renewability by simple mechanical polishing. The recovery rates observed were highly concordant with those obtained for high-performance liquid chromatography, having a relative standard deviation of less than 1.3%.