Magnetic solid-phase extraction of Zineb by C18-functionalised paramagnetic nanoparticles and determination by first-derivative spectrophotometry

Fe₃O₄-SiO₂-C₁₈ paramagnetic nanoparticles have been synthesised and used as magnetic solid-phase extraction (MSPE) sorbent for the extraction of Zineb from agricultural aqueous samples under ultrasonic condition and quantified through a first-derivative spectrophotometric method. The produced magnetic nanoparticles were characterised by using scanning electron microscopy, X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy and zeta potential reader. The Fe₃O₄-SiO₂-C₁₈ paramagnetic nanoparticles had spherical structures with diameters in the range of 198–201 nm. Further, MSPE was performed by dispersion of Fe₃O₄-SiO₂-C₁₈ paramagnetic nanoparticles in a buffered aqueous solution accompanied by sonication. Next, the sorbents were accumulated by applying an external magnetic field and were washed with 4-(2-pyridylazo) resorcinol-dimethyl sulfoxide solution, for the purpose of desorbing the analyte. The extraction conditions (sample pH, washing and elution solutions, amount of sorbents, time of extraction, sample volume and effect of diverse ions), as well as Zineb-PAR first-order derivative spectra, were also evaluated. The calibration curve of the method was linear in the concentration range of 0.055–24.3 mg L^?1 with a correlation coefficient of 0.991. The limit of detection and limit of quantification values were 0.022 and 0.055 mg L^?1, respectively. The precision of the method for 0.27 mg L^?1 solution of the analyte was found to be less than 3.2%. The recoveries of three different concentrations (0.27, 1.37 and 13.7 mg L^?1) obtained 98.3%, 98.5% and 96.0%, respectively. The proposed Fe₃O₄-SiO₂-C₁₈ paramagnetic nanoparticles were found to have the capability of reusing for 7.0 times.     

Ligandless-ultrasound-assisted emulsification microextraction followed by inductively coupled plasma-optical emission spectrometry for simultaneous determination of heavy metals in water samples

In this study, a simple and efficient method of ligandless-ultrasound-assisted emulsification microextraction (LL-USAEME) followed by inductively coupled plasma-optical emission spectrometry (ICP-OES) has been developed for simultaneous extraction, preconcentration and determination of manganese, cadmium, cobalt and nickel in water samples. In the proposed approach, tetrachloroethylene was selected as extraction solvent. The effect of important experimental factors such as volume of extraction solvent, pH, sonication time, salt concentration, and temperature was investigated by using a fractional factorial design (2^5?1) to identify important factors and their interactions. In the next step, a Box-Behnken design (BBD) was applied for optimisation of significant factors. The obtained optimal conditions were: 30?µL for extraction solvent, 12 for pH, 5?min for sonication time, and 5% w/v for salt concentration. The limits of detections (LODs) for Cd(II), Co(II), Mn(II) and Ni(II) were 0.20, 0.13, 0.21 and 0.28?µg?L^?1, respectively. Relative standard deviations (RSD, C?=?200.0?µg?L^?1, n?=?9) were between 3.4–7.5% and the calibration graphs were linear in the range of 0.25 to 1000.0?µg?L^?1 for Mn, 0.5–1000.0?µg?L^?1 for Co and Ni and 1.0–250.0?µg?L^?1 for Cd. The determination coefficients (R ²) of the calibration curves for the analytes were in the range of 0.993 to 0.999. The proposed method was validated by using two certified reference materials, and also the method was applied successfully for the determination of heavy metals in different real water samples.     

Evaluation of the corrosion inhibition effect of micro/nanocapsulated polymeric coatings: a comparative study by use of EIS and Tafel experiments and the area under the Bode plot

In this paper we propose an approach for ranking self-healing polymeric coatings containing micro/nanocapsules in order of corrosion-protection effectiveness on exposure to 3.5 % (w/w) NaCl solution. The results indicated that development of electrochemical cells was inhibited by the active components of the ruptured embedded inhibitor micro/nanocapsules which were released into a scratch inflicted in the polymeric coating on steel surface. Undamaged surface film of test and control specimens exposed to the solution had excellent corrosion-inhibition performance, as reflected by results from both electrochemical impedance spectroscopy and polarization tests. Moreover, three coatings containing capsules synthesized at three different agitation rates with the same thickness were compared to determine the optimum rate. For the optimum rate the optimum thickness was then determined. The areas under Bode plots were determined and used as useful values for evaluation and ranking the coatings. It was found that the area under the Bode plot is a good criterion for evaluating polymeric coating degradation during immersion. There was good agreement between the results of this work and those from electrochemical tests.     

Synthesis,crystal structure,and electrochemical properties of Ni(II) and Cu(II) complexes with two unsymmetrical N2O2 Schiff base ligands

Nickel(II) and copper(II) complexes of two unsymmetrical tetradentate Schiff base ligands [Ni(Me-salabza)] (1), [Cu(Me-salabza)] (2) and [Ni(salabza)] (3), {H₂salabza = N,N′-bis[(salicylidene)-2-aminobenzylamine] and H₂Me-salabza = N,N′-bis[(methylsalicylidene)-2-aminobenzylamine]}, have been synthesized and characterized by elemental analysis and spectroscopic methods. The crystal structures of 2 and 3 complexes have been determined by single crystal X-ray diffraction. Both copper(II) and nickel(II) ions adopt a distorted square planar geometry in [Cu(Me-salabza)] and [Ni(salabza)] complexes. The cyclic voltammetric studies of these complexes in dichloromethane indicate the electronic effects of the methyl groups on redox potential.     

Potentiometric and spectroscopic studies of three new mixed inorganic–organic hybrid materials based on Preyssler and Wells–Dawson heteropolyoxometalates containing proline, leucine, and asparagine

Three new organic–inorganic hybrid materials based on two important heteropolyoxometalates namely Preyssler (=K_12.5H_1.5[Na(H₂O)P₅W₃₀O₁₁₀]·35H₂O) and Wells–Dawson (=K₆[P₂W₁₈O₆₂]·10H₂O) anions, namely, (Hpro)₉(Hleu)₃K₂[Na(H₂O)P₅W₃₀O₁₁₀]·25H₂O (1), (Hpro)₄(Hasp)[HP₂W₁₈O₆₂]·20H₂O (2), and (Hpro)₁₁K₃[Na(H₂O)P₅W₃₀O₁₁₀]·18H₂O (3) where pro, leu, and asp are proline, leucine, and asparagine, respectively, were prepared and identified by elemental analysis, infrared and proton nuclear magnetic resonance spectroscopies, and thermogravimetric analysis. The hybrid materials are made up of positively charged amino acids, [Na(H₂O)P₅W₃₀O₁₁₀]^14? and [P₂W₁₈O₆₂]^6? anions, and H₂O molecules of crystallization. These constituents’ fragments held together into a three-dimensional supermolecular network through non-covalent interactions. The protonation constants of the amino acids used, and Preyssler and Wells–Dawson species in all possible protonated forms, the equilibrium constants for binary systems of proline–asparagine and proline–leucine, and the stoichiometry and stability constants of the corresponding binary and ternary hybrids with Preyssler and Wells–Dawson heteropolyoxometalates in aqueous solution were investigated by potentiometric pH titration method. The stoichiometries of the most hybrid species in solution were compared with the corresponding hybrids in the solid phase, in detail.     

Novel and versatile methodology for synthesis of β-aryl-β-mercapto ketone derivatives as potential urease inhibitors

The objective was to obtain new scaffold of compounds possessing anti-urease activity. For this new and simple method for the synthesis of β-aryl-β-mercapto ketone derivatives based on Michael addition of thiophenol to chalcones in an ionic liquid as a solvent was improved. The products were obtained in good to moderate yields with high purity and characterized by spectral and elemental analyses. The activities of synthesized compounds were investigated as new inhibitors of jack bean urease. Among 22 synthesized compounds, all of them have shown inhibitory effect in micromolar range, and the most potent one has IC₅₀ = 6 μM compared to hydroxyurea IC₅₀ = 100 μM as a reference inhibitor. A docking study was performed using Autodock 4.2 in parallel to in vitro experiments to illustrate the corresponded binding affinities as well as binding site, and involved residues in interaction. These computational results complimented the experimental inhibition activity and enabled us to report a potent urease inhibitors based on β-aryl-β-mercapto ketone scaffold.     

Application of gold-labeled antibody biosensor in simultaneous determination of total aflatoxins using artificial neural network

Preparation of antibody-coated gold nanoparticles (GNPs) specific to aflatoxins B1, B2, G1 and G2 and its use in developing aflatoxins diagnostic method were presented in this paper. The formation of gold-labeled antibodies was accomplished at optimal condition. Due to severe overlapping between the emission profiles for the aflatoxins, they cannot be determined by direct inspection of data. The strategy used in this study, constituted by artificial neural network (ANN), was easy to implement and to originate reliable results. ANN can be successfully applied to spectrofluorimetric spectra matrices to simultaneous determination of total aflatoxins. Quantitative results obtained using ANN method for aflatoxins in pistachio nuts samples were compared to those obtained using the HPLC method. Obtained results using these two methods did not show significant differences.     

Solvent-free one-pot synthesis of 4-aryl-3,5-dimethyl-1,4,7,8-tetrahydrodipyrazolo[3,4-b:4′,3′-e]pyridines using Fe3O4@SiO2@(BuSO3H)3 catalytic Fe3+ system as selective colorimetric

Research on Chemical Intermediates - The synthesis of 4-Aryl-(3,5-dimethyl-1,4,7,8-tetrahydro-dipyrazolo[3,4b:4′,3′e]pyridine derivatives was accomplished using Fe3O4@SiO2@(BuSO3H)3...     

Label-free PSA electrochemical determination by seed-mediated electrochemically-deposited gold nanoparticles on an FTO electrode

Journal of Solid State Electrochemistry - A facile and sensitive approach is introduced to precisely determine trace amounts of prostate specific antigen (PSA) by gold nanostructures deposited on...     

Reaction between alkyl isocyanides and isopropylidene Meldrum’s acid in the presence of bidentate nucleophiles

Summary The reaction between alkyl isocyanides and isopropylidene Meldrum’s acid in the presence of 1,2-ethanediol leads to N ¹-(alkyl)-2-(5,7-dioxo-1,4-dioxepane-6-yl)-2-methylpropanamides. 1,3-Propanediol or 1,4-butanediol produce hydroxyalkyl 1-(tert-butyl)-4,4-dimethyl-2,5-dioxo-3-pyrrolidinecarboxylates. When the reaction was performed in the presence of catechol, bis(2-hydroxyphenyl) 2-[2-(tert-butylamino)-1,1-dimethyl-2-oxoethyl]malonate was obtained. 2-Aminophenols react with alkyl isocyanides in the presence of isopropylidene Meldrum’s acid to produce 1-alkyl-N ³-(2-hydroxyaryl)-4,4-dimethyl-2,5-dioxo-3-pyrrolidinecarboxamides in good yields.