Application of Pneumatic Flow Injection-Tandem Spectrometer System for Chromium Speciation

In this approach, a pneumatic flow injection-tandem spectrometer system, without a delivery pump, has been developed to study chromium speciation. In this system, suction force of pneumatic nebulizer of a flame atomic absorption spectrometer has been used for solution delivery through the manifold. Cr(VI) and total Cr concentrations were determined using UV-Vis and FAAS spectrometers, respectively. The Cr(III) was determined by difference. The calibration curves were linear up to 10 μg mL−1 and 20 μg mL−1 for Cr(VI) and total Cr with detection limit of 0.12 μg mL−1 and 0.07 μg mL−1 for Cr(VI) and Cr(III), respectively. The midrange precision and accuracy are less than 1.98% and ± 2.50% for two species, respectively, at a sampling rate of 100 h−1. This system was applied for the determination of the chromium species in spiked and natural waters as well as industrial waters

A simple strategy to increase inhibitory activity of chitosan towards iron corrosion in acidic media

227-234The chitosan as a natural and inexpensive polymer is considered as an appropriate choice towards the corrosion inhibitory. Here, the corrosion and inhibition efficacy of iron sheets is examined in the H2SO4 solution and the presence of chitosan and potassium iodide as an inhibitor through gravimetry, potentiodynamic polarization, and impedance analyses. The inhibition performance is found to be enhanced by adding chitosan concentration. The experimental data demonstrate that the doping iodide ion to chitosan is efficient on the surface coverage and the inhibition performance. The introduced inhibitors are of the interface inhibitors → liquid phase → mixed type with the physical adsorption. The adsorption of iodized chitosan on the iron surface is followed Langmuir isotherm. These inhibitors, by changing the electrical double layer, increase the resistance of charge transfer. The existence of iodide in the chitosan structure improves the electron density of polymer and strengthens the interaction between inhibitor and metal

A simple strategy to increase inhibitory activity of chitosan towards iron corrosion in acidic media

The chitosan as a natural and inexpensive polymer is considered as an appropriate choice towards the corrosion inhibitory. Here, the corrosion and inhibition efficacy of iron sheets is examined in the H2SO4 solution and the presence of chitosan and potassium iodide as an inhibitor through gravimetry, potentiodynamic polarization, and impedance analyses. The inhibition performance is found to be enhanced by adding chitosan concentration. The experimental data demonstrate that the doping iodide ion to chitosan is efficient on the surface coverage and the inhibition performance. The introduced inhibitors are of the interface inhibitors → liquid phase → mixed type with the physical adsorption. The adsorption of iodized chitosan on the iron surface is followed Langmuir isotherm. These inhibitors, by changing the electrical double layer, increase the resistance of charge transfer. The existence of iodide in the chitosan structure improves the electron density of polymer and strengthens the interaction between inhibitor and metal

Adsorptive Removal of Benzene and Toluene from Aqueous Environments by Cupric Oxide Nanoparticles: Kinetics and Isotherm Studies

Removal of benzene and toluene, as the major pollutants of water resources, has attracted researchers’ attention, given the risk they pose to human health. In the present study, the potential of copper oxide nanoparticles (CuO-NPs) in eliminating benzene and toluene from a mixed aqueous solution was evaluated. For this, we performed batch experiments to investigate the effect of solution pH (3–13), dose of CuO-NPs (0.1–0.8 g), contact time (5–120 min), and concentration of benzene and toluene (10–200 mg/l) on sorption efficiency. The maximum removal was observed at neutral pH. By using the Langmuir model, we measured the highest adsorption capacity to be 100.24 mg/g for benzene and 111.31 mg/g for toluene. Under optimal conditions, adsorption efficiency was 98.7% and 92.5% for benzene and toluene, respectively. The sorption data by CuO-NPs well fitted into the following models: Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich model. The experimental information well fitted in the Freundlich for benzene and Langmuir for toluene. Based on the results, adsorption followed pseudo-second-order kinetics with acceptable coefficients. The findings introduced CuO-NPs as efficient compounds in pollutants adsorption. In fact, they could be used to develop a simple and efficient pollutant removal method from aqueous solutions

Au Nanoparticles on 4-Thiophenol-Electrodeposited Carbon Surfaces for the Simultaneous Detection of 8-Hydroxyguanine and Guanine

In this proof-of-concept study, gold nanoparticles (AuNPs) were immobilized on glassy carbon electrode (GCE) surfaces using a surface-anchored diazonium salt of 4-aminothiophenol (GCE-Ph-S-AuNPs). X-ray photoelectron spectroscopy (XPS) studies confirmed the attachment of the AuNPs via 4-thiophenol onto the surface of the modified electrode. Differential pulse voltammetry (DPV) was performed for the simultaneous determination of guanine (G) and 8-hydroxyguanine (8-OH-G). The calibration curves were linear up to 140 µM and 60 µM with a limit of detection of 0.02 µM and 0.021 µM for G and 8-OH-G, respectively. Moreover, chronoamperometric studies were carried out for the determination of diffusion coefficients of 8-OH-G and G. The GCE-Ph-S-AuNPs were also applied in genomic DNA-spiked samples for the determination of G and 8-OH-G with recovery rates between 98.5% and 103.3%. The novel electrochemical surface provided a potential platform for the sensitive detection of 8-OH-G related to oxidative stress-induced DNA damage in clinical studies

Presentation of anodic electrocatalyst for polymeric fuel cell: Pt nanoparticles immobilized on NdFeO3 nanocrystals and carbon nanotubes

9-22Current catalysts for the methanol oxidation in fuel cells (typically noble metals-based) are susceptible to poisoning with intermediates like CO. Hence superseded catalysts have been desirable for methanol oxidation based on incorporation of mixed oxides. The different types of nanocomposites have been prepared with Pt nanoparticles (PtNPs), functionalized CNTs, perovskite NdFeO3 nanoparticles (NdFeO3NPs) and chitosan (CH) polymer and their catalytic activity toward methanol oxidation have been investigated by the electrochemical studies. The equations of current density versus time are obtained via the fitting and simulation of experimental data. In the following, the amount of transferred charge during methanol oxidation versus time has been calculated through the lower Riemann sum of curve correspond to experimental data and the integration of mentioned equations both. A direct methanol fuel cell (DMFC) is designed, assembled and tested with the suggested PtNPs-CNTs-NdFeO3NPs-CH nanocomposites as an anodic catalyst at variety conditions. The effect of experimental factors on DMFC performances has been investigated and optimized

Nanocomposite of Ellagic Acid with Multi-Walled Carbon Nanotubes for the Simultaneous Voltammetric Detection of Six Biomolecules

In this proof-of-concept study, a highly sensitive electrochemical sensor using a graphite paste electrode modified with ellagic acid and multi-walled carbon nanotubes (MGPE/MWCNTs-EA) was developed for the simultaneous determination of six biomolecules: ascorbic acid (AA), dopamine (DA), uric acid (UA), tryptophan (Trp), xanthine (XA), and caffeine (CA). Differential pulse voltammetry (DPV) was performed at a potential range from 0.1–1.2 V vs. Ag/AgCl in phosphate electrolyte (pH 2.0). The modified GPE enabled the simultaneous determination of biomolecules under investigation in human urine and blood serum samples with detection limits ranging from 11–91 nM with recoveries of 94.0–106.0%. The electrochemical performance of the modified GPE for the analytes was stable and reproducible and checked with standard high performance liquid chromatography technique. The data suggested that the modified GPE provided a promising platform for routine quantitative determination of the biomolecules under investigation in quality control studies of real samples collected from food and pharmaceutical products

Graphene Oxide Nanoribbons in Chitosan for Simultaneous Electrochemical Detection of Guanine, Adenine, Thymine and Cytosine

Herein, graphene oxide nanoribbons (GONRs) were obtained from the oxidative unzipping of multi-walled carbon nanotubes. Covalent coupling reaction of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) and N-hydroxy succinimide (NHS) with amine functional groups (-NH2) of the chitosan natural polymer (CH) was used for entrapping GONRs on the activated glassy carbon electrode (GCE/GONRs-CH). The nanocomposite was characterized by high-resolution transmission electron microscopy (HRTEM), and field-emission scanning electron microscopy (FESEM). In addition, the modification steps were monitored using FTIR. The nanocomposite-modified electrode was used for the simultaneous electrochemical determination of four DNA bases; guanine (G), adenine (A), thymine (T) and cytosine (C). The nanocomposite-modified GCE displayed a strong, stable and continuous four oxidation peaks during electrochemistry detection at potentials 0.63, 0.89, 1.13 and 1.27 V for G, A, T and C, respectively. The calibration curves were linear up to 256, 172, 855 and 342 μM with detection limits of 0.002, 0.023, 1.330 and 0.641 μM for G, A, T and C, respectively. The analytical performance of the GCE/GONRs-CH has been used for the determination of G, A, T and C in real samples and obtained a recovery percentage from 91.1%–104.7%. Our preliminary results demonstrated that GCE/GONRs-CH provided a promising platform to detect all four DNA bases for future studies on DNA damage and mutations

Hybrid Nanomaterial of Graphene Oxide Quantum Dots with Multi-Walled Carbon Nanotubes for Simultaneous Voltammetric Determination of Four DNA Bases

In this proof-of-concept study, a novel hybrid nanomaterial-based electrochemical sensor was developed for the simultaneous detection of four DNA bases. For the modification of the working electrode surface, graphene oxide quantum dots (GOQDs) were synthesized using a solvothermal method. GOQDs were then used for the preparation of a hybrid nanomaterial with multi-walled carbon nanotubes (GOQD-MWCNT) using a solvothermal technique for the first time. Transmission electron microscopy (TEM) was used to characterize the GOQDs-MWCNTs. A glassy carbon electrode (GCE) was modified with the GOQDs-MWCNTs using Nafion™ to prepare a GOQD-MWCNT/GCE for the simultaneous determination of four DNA bases in phosphate buffer solution (PBS, pH 7.0) using differential pulse voltammetry (DPV). The calibration plots were linear up to 50, 50, 500, and 500 µM with a limit of detection at 0.44, 0.2, 1.6, and 5.6 µM for guanine (G), adenine (A), thymine (T) and cytosine (C), respectively. The hybrid-modified sensor was used for the determination of G, A, T, and C spiked in the artificial saliva samples with the recovery values ranging from 95.9 to 106.8%. This novel hybrid-modified electrochemical sensor provides a promising platform for the future development of a device for cost-effective and efficient simultaneous detection of DNA bases in real biological and environmental samples