Lanthanum-selective sensors based on 3-amino-2-mercapto-3H-quinazolin-4-one in PVC matrix

A new solvent polymeric membrane (PME) and coated graphite (CGE) electrodes based on 3-amino-2-mercapto-3H-quinazolin-4-one as a suitable carrier for La(III) ion are described. The sensors exhibited a Nernstian response for La(III) ion over a wide concentration range (3.0 × 10^?7 to 1.0 × 10^?1 M for PME and 1.0 × 10^?7 to 1.0 × 10^?1 M for CGE) with a slope of 20.1 ± 0.3 (PME) and 23.4 ± 0.4 (CGE) mV decade^?1. The lower detection limits by PME and CGE were 2.0 × 10^?7 and 7.1 × 10^?8 M, respectively. The potentiometric response of the proposed electrodes was independent of the pH of the test solution in the pH range 3.0–9.0 with a fast response time (<10 s). The applications of prepared sensors were demonstrated in the determination of lanthanum ions in spiked water sample and also utilized for indirect determination of fluoride content of two mouth wash preparation samples.     

Determination of Hg(II) in Environmental Water Samples Using DLLME Method Prior to GC-FID

Mercury exists in two forms in environment, inorganic salts and organic compounds. Determination of mercury is very important, due to its health effects. In the present research, diphenylation of mercury using phenylboronic acid as a derivatization reagent was used for the determination of Hg(II) in real water samples. A simple, rapid and cheap method named dispersive liquid–liquid microextraction was used for the extraction of analyte under the following conditions: extraction solvent 16 μL of carbon tetrachloride, disperser solvent 1 mL of ethanol and sample volume 5 mL. Under the optimal conditions, the enrichment factor for diphenylmercury was 931 and the limit of detection calculated on the basis of five replicates was 0.004 μg mL^?1. The repeatability of the method expresses as relative standard deviation was 5.1 (n = 6). The linear range was between 0.01 and 10 μg mL^?1. The performance of the proposed technique was evaluated for the determination of mercury in different environmental water samples.     

Synthesis of Novel Organosilicon Compounds Possessing Fully Substituted Imidazole Nucleus Sonocatalyzed by Fe-Cu/ZSM-5 Bimetallic Oxides

An efficient four-component synthesis of 1,2,4,5-tetrasubstituted imidazoles is described by one-step condensation of an aldehyde, benzil, ammonium acetate, and primary aromatic amine with nanostructure Fe-Cu/ZSM-5 bimetallic oxides in water under ultrasonic irradiation. The short reaction time, good yields, environmental friendly procedure, mild reaction conditions, and convenient operation are important advantage of this protocol. The products generated during the study have been utilized as substrates for synthesis of organosilicon-containing imidazoles. Synthesis of tris(triorganosilyl)methylimidazole derivatives were carried out using organolithium reagent (Me₃Si)₃CLi, prepared via metalation of (Me₃Si)₃CH with methyllithium in tetrahydrofuran, in excellent yields.     

Oxidation of 1,4-Dihydropyridines under Mild and Heterogeneous Conditions

A combination of NaHSO₄.H₂O and NaNO₂ in the presence of wet SiO₂ was used as an effective oxidizing agent for the oxidation of dihydropyridines to their corresponding pyridine derivatives at room temperature with excellent yields.     

Synthesis of Functionalized Pyrroles by Reaction of 3,4‐Diacetylhexane‐2,5‐dione with Primary Amines in Water

3,4‐Diacetylhexane‐2,5‐dione (tetra‐acetylethane) undergoes a complex reaction with primary amines in boiling water to produce N‐alkyl‐3‐acetyl‐2,5‐dimethylpyrroles, together with small quantities of N‐alkyl‐3,4‐diacetyl‐2,5‐dimethylpyrroles and 2,5‐dimethyl‐1H‐pyrrol‐3‐yl‐vinyl‐acetamides. When the reaction was carried out in methanol at room temperature, the yields of the latter products increased.     

Synthesis of Diaryl Ethers Through the Copper-Catalyzed Arylation of Phenols with Aryl Iodides Using KF/Al2O3

An efficient synthesis of diaryl ethers by the copper-catalyzed arylation of phenols with a variety of aryl iodide susing KF/Al₂O₃ as a suitable base and CuI and 1,3 diphenyl-1,3 propandione as the catalyst is described.     

Solvent‐Free Chemoselective Synthesis of 1,1‐Diacetates Catalyzed by Cu(NO3)2 · 3H2O

1,1‐Diacetates have been synthesized by the reaction of a variety of aldehydes with acetic anhydride in the presence of cupric nitrate as catalyst under solvent‐free conditions. Ketones were not converted to the corresponding diacetates under these conditions.     

Characterization of Chitosan/Alginate Self-Assembled Nanoparticles as a Protein Carrier

The aim of this study was to evaluate the effect of the polymeric ratios on the characteristics of chitosan/alginate (ch/alg) self-assembled nanoparticles and their potential as protein delivery vehicle. The nanoparticles were prepared using proper mixing of polymers in presence or absence of bovine serum albumin (BSA) as a protein model. Three formulations of nanoparticles comprising ch/alg ratios of 2:1, 1:1, and 1:2 were prepared. Size, shape and zeta potential of the formulations were studied by scanning electron microscopy (SEM) and nanosizer instruments. FTIR, and differential scanning calorimetery (DSC) studies were performed to investigate polymer-polymer or polymer-protein interactions. Release profiles and entrapment efficiencies of the nanoparticles were determined by calorimetric technique using appropriate techniques. Entrapment efficiency was 70% for ch/alg ratio of 1:1, 65% for 1:2, and 60% for 2:1. The z-average size of the nanoparticles were 403, 205, and 318 nm for ch/alg ratios of 2:1, 1:1, and 1:2, respectively. Average zeta potentials were ?47, +15, ?25 mV for 2:1, 1:1, and 1:2 as well. Considering the favorable features required for protein delivery systems, ch/alg (1:1) due to its smallest size, highest loading, and most homogenous shape was regarded as the best ratio.     

Determination trace amounts of thallium after separation and preconcentration onto nanoclay loaded with 1-(2-pyridylazo)-2-naphthol as a new sorbent

A procedure has been proposed for the separation and preconcentration of trace amounts of thallium. It is based on the adsorption of thallium ions onto organo nanoclay loaded with 1-(2-pyridylazo)-2-naphthol (PAN). Thallium ions were quantitatively retained on the column in the pH range of 3.5–6.0, whereas quantitative desorption occurs with 5.0?mL of 5% ascorbic acid and thallium was determined by flame atomic absorption spectrometry. Linearity was maintained between 0.66?ng?mL^?1–15.0?µg?mL^?1?in initial solution. Detection limit was 0.2?ng?mL^?1?in initial solution and preconcentration factor was 150. Eight replicate determinations of 2.0?µg?mL^?1 of thallium in final solution gave a relative standard deviation of ±1.48%. Various parameters have been studied, such as the effect of pH, breakthrough volume and interference of a large number of anions and cations and the proposed method was used to determine thallium ions in water and standard samples. Determination of thallium ions in standard sample showed that the proposed method has good accuracy.     

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.