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• Magnetic MWCNTs coated with poly 8-hydroxyquinoline (MWCNTs/Fe 3 O 4 @PHQ) nanocomposite was prepared and characterized. • It was used as a novel adsorbent in dispersive micro-solid phase extraction (D-μ-SPE) method. • D-μ-SPE-GC method was successfully applied for the determination of OPPs pesticides in various real samples. • This method was proved to be fast, efficient and sensitive. This study presents a dispersive micro-solid phase extraction (D-μ-SPE) approach for extracting and determining of two organophosphorus pesticides (OPPs), including diazinon and chlorpyrifos as model analytes in various samples. For this purpose, we synthesized, characterized, and utilized magnetic multi-walled carbon nanotubes coated with poly 8-hydroxyquinoline (MWCNTs/Fe 3 O 4 @PHQ) as a novel sorbent. The impact of various parameters, including sorbent type, sample pH, sample volume, sorbent amount, desorption solvent (type and volume), extraction time, and ionic strength on the extraction efficiency was investigated and optimized. Following the extraction, the desorbed pesticides in acetone were analyzed using gas chromatography with an FID detector. Under the optimized experimental conditions, the proposed method showed excellent linearity in the range of 3–1000 µg/L, low detection limit (0.9–1.5 µg/L), good relative recoveries (86–101.5 %), and high precision (RSD < 6.5 %). Finally, the applicability of this method was evaluated by analyzing the target OPPs in a variety of real samples, and obtained satisfactory results. [ABSTRACT FROM AUTHOR]

A high performance electrochemical sensor for the detection of methamphetamine (MA) at the gold nanoparticle (GNP)/multiwalled carbon nanotube (MWCNT)-Nafion (Nf) modified screen printed electrode (SPE) is reported. Gold nanoparticles were electrodeposited on the substrate using a constant potential. Energy dispersive X-ray (EDX) spectrum and mapping and also scanning electron microscopy (SEM) results showed that GNPs were deposited and dispersed uniformly on the SPE/MWCNTs-Nf-Nf, respectively. The electrochemical behavior of MA was studied by cyclic voltammetry (CV), and modified electrode was used for the determination of sub-nanomolar amounts of MA in samples using square wave stripping voltammetry (SWSV) and electrochemical impedance spectroscopy (EIS). Under the optimized experimental conditions, the modified SPE revealed broad linear ranges of 0.02–0.1 and 3.0–50 μM (LOD = 6 nM) for SWSV and 1.15–26.9 nM (LOD = 0.3 nM) for EIS. Finally, the SPE/MWCNTs-Nf/GNPs showed stable electrochemical cyclic voltammetry responses. The high performances of the novel MA impedimetric sensor are mainly attributed to high surface area-to-volume ratio, excellent conducting capability and interface-dominated properties of GNPs which in combination with special properties of MWCNTs provide an effective modifier for MA oxidation. Moreover, using sensitive methods like impedimetric and stripping results in excellent responses. [ABSTRACT FROM AUTHOR]

In this study, a hybrid nanocomposite consisting of a conducting polymer and gold nanoparticles (AuNPs) is fabricated on a multi-walled carbon nanotubes modified glassy carbon electrode (MWCNTs/GCE). First, dihydroxy-benzene derivative (4,5-dihydro-1,3-thiazol-2-ylsulfanyl-1,2-benzenediol) containing sulphur and nitrogen groups was electrochemically synthesized and used as a monomer. Then, a thin layer of conducting polymer is coated electrochemically on a MWCNTs/GCE and the effective parameters have been optimized. Afterward, the nano-sized AuNPs are embedded by physical adsorption from colloidal solution of AuNPs. The resultant nanocomposite modified electrode is characterized by electrochemical methods and transmission electron microscopy. Finally, the potential application of nanocomposite film modified electrode has been investigated for the electrocatalytic oxidation of hydrazine. The experimental results showed that the response of modified electrode is linear in the range of 2.0–350.0 μM with detection limit (S/N = 3) of 0.6 μM for hydrazine. [ABSTRACT FROM AUTHOR]

Highlights: [•] SPE–EME was developed for ultra-preconcentration of chlorophenoxy acid herbicides. [•] Graphene oxide was used as sorbent in SPE step. [•] Significant factors affecting on EME were optimized with the Box–Behnken design. [•] An efficient separation was obtained with capillary electrophoresis. [•] Good enrichment factors were found in the range of 1950–2000. [ABSTRACT FROM AUTHOR]

Abstract: In the present work, for the first time, electromembrane extraction (EME) combined with differential pulse voltammetry by multi-wall carbon nanotubes modified screen-printed carbon electrode has been reported for determining sufentanil. EME of sufentanil was carried out by applying a D.C. electrical potential through a thin supported liquid membrane (SLM). Charged drug molecules were extracted from an aqueous sample, through the SLM, into an acidic aqueous acceptor solution (20μL) which is placed inside the lumen of a hollow fiber. Then, the acceptor solution was analyzed using differential pulse voltammetry (DPV). A Box–behnken design was used in order to optimize different variables affecting extraction efficiency using following DPV currents as signals. The main parameters which affect the extraction and determination of sufentanil were observed to be: accumulation time, 30s; organic solvent, 2-nitrophenyl octyl ether; pH of the donor phase, 2.5; pH of the acceptor phase, 1.0; extraction time, 28min; extraction output potential difference, 190V and stirring rate, 1000rpm. Under the optimal conditions, DPV currents were linear with the concentration of sufentanil within the range of 6.4×10−8–3.62×10−6 moldm−3 with the detection limit (S/N=3) of 2.0×10−8 moldm−3. Finally, the proposed method has been successfully used for the determination of sufentanil in urine and plasma samples. [Copyright &y& Elsevier]

Abstract: In this work, a heterogeneous catalyst based on palladium nanoparticles encapsulated on polyamidoamine dendrimer-grafted multi-walled carbon nanotubes (PdNPs/PAMAM–MWCNTs) hybrid material was used as an electrode modifier. The catalyst was dissolved in N,N-Dimethylformamide (DMF) and immobilized on the surface of glassy carbon electrode using drop casting method to fabricate PdNPs/PAMAM–MWCNTs modified electrode. The modified electrode showed good catalytic activity for the electrooxidation of oxalic acid in 0.1M HClO4 with a substantial decrease in anodic overpotentials (450mV) and increase in anodic peak current (about 3 times) in comparison with unmodified electrode. The values of electron transfer coefficients (α =0.37) and diffusion coefficient (D =2.12×10−6 cm2 s−1) were calculated for oxalic acid using electrochemical approaches. The cyclic voltammetry showed a linear response in the range of 0.03–5.0mM with detection limit (3σ) of 0.02mM for oxalic acid. The experimental results also showed that the sensor has good reproducibility (R.S.D=4.3% for 5.0mM, n =5), long-term stability (over than 100 analysis with intermittent use), and a fast response time (5s). Finally, the modified electrode was successfully applied to determine the oxalic acid content in spinach. [Copyright &y& Elsevier]

Abstract: Electrochemical oxidation of catechols (1a–c) has been studied in the presence of methyl acetoacetate (2a) and ethyl acetoacetate (2b) as nucleophiles in aqueous solution using cyclic voltammetry and controlled-potential coulometry. The results indicate that the quinones derived from catechols (1a–c) participate in Michael addition reactions with 2a and 2b to form the corresponding benzofuran derivatives (3a–f). The electrochemical synthesis of 3a–f has been successfully performed in an undivided cell in good yield and purity. The oxidation mechanism was deduced from voltammetric data and by coulometry at controlled potential. The products have been characterized after purification by IR, 1H NMR, 13C NMR, MS, and single crystal X-ray diffraction. [Copyright &y& Elsevier]

Abstract: 5,6,14,15-Dibenzo-1,4-dioxa-8,12-diazacyclopentadeca-5,14-diene (DBDA15C4) as a mobile carrier and histidine as a stripping agent were used for the selective uphill and proton driven transport of Zn2+ ions through a bulk liquid membrane. A study of different parameters on zinc transport has been carried out. This include the pH of the feed phase, amount of DBDA15C4 in the liquid membrane, type and concentration of acid and amino acid in the strip phase and transport. In the optimum procedure conditions, the maximum transport of Zn2+ ions at 3h was observed (96.2±1.2%). With this system, Zn2+ as Zn-histidine complex could be separated from Cu2+, Cd2+, Pb2+, Mn2+, Cr3+, Al3+, Co2+, Ni2+, Ca2+, Mg2+ and Fe3+. The transport mechanism of this system has been described. [Copyright &y& Elsevier]

Abstract: Electrochemical oxidation of catechols (1a–1c) has been studied in the presence of 4-hydroxy-1-methyl-2(1H)-quinolone (3) as a nucleophile in aqueous solution using cyclic voltammetry and controlled-potential coulometry. The results indicate that the quinones derived from catechols (1a–1c) participate in Michael addition reactions with 3 to form the corresponding benzofuran (or isochromeno[4,3-c]quinoline) derivatives (6a–6c). The electrochemical synthesis of (6a–6c) has been successfully performed in an undivided cell in good yield and purity. The oxidation mechanism was deduced from voltammetric data and by coulometry at controlled-potential. The products have been characterized after purification by IR, 1H NMR, 13C NMR and MS. [Copyright &y& Elsevier]

Abstract: A novel sensitive chromogenic reagent, N,N′-bis(3-methylsalicylidene)-ortho-phenylene diamine (MSOPD), has been synthesized and used in the spectrophotometric determination of nickel. At pH 8, MSOPD can react with nickel ion at room temperature to form a 1:1 complex. The apparent molar absorptivity is 9.5×104 lmol−1 cm−1 at 430nm. Beer''s low is obeyed over the range 0–1.0×10−5 M of nickel with a detection limit of 1.36×10−8 M. The relative standard deviation for measurement of 3.41×10−6 M nickel is 1.3% (n =10). The method has successfully been applied to determination of trace amounts of nickel in some natural food samples. [Copyright &y& Elsevier]

Abstract: Electrochemical oxidation of 2,3-dimethylhydroquinone 1 has been studied in the presence of o-phenylenediamines 3a–c as nucleophiles in aqueous solution, using cyclic voltammetry and controlled potential coulometry. The results indicate that the quinone 2 derived from 2,3-dimethylhydroquinone participates in Michael addition and imine condensation reactions with o-phenylenediamine via an ECECC mechanism, and is converted to the corresponding phenazine derivatives 7a–c and 7′b. The electrochemical synthesis of compounds 7a–c and 7′b has been performed successfully at a carbon rod electrode in an undivided cell with good yields and high purities. [Copyright &y& Elsevier]

Highlights: [•] d-Amino acids are mostly considered futile or toxic to plant cells metabolism. [•] Herein, d-Orn is shown to participate in selected biosynthetic pathways in tobacco. [•] l-Arg was the only AA which was selectively accumulated in d-Orn treated cells. [•] Results indicate that a previously unknown pathway is related to the role of d-Orn. [•] This pathway can be potently applied to produce l-Arg in the plant cells. [ABSTRACT FROM AUTHOR]

Abstract: Electrochemical oxidation of o-dihydroxybenzenes (1a and 1b) has been studied in the presence of 4-hydroxy-1-methyl-2(1H)-quinolone (3) as a nucleophile in aqueous solution using cyclic voltammetry and controlled-potential coulometry. The results indicate that the o-quinones derived from o-dihydroxybenzenes (1a and 1b) participate in 1,4-(michael) addition reactions with 3 to form the corresponding new o-dihydroxybenzene derivatives (6a and 6b). We propose a mechanism for the electrode process. The efficient electrochemical synthesis of 6a and 6b has been successfully performed at carbon rod electrodes in an undivided cell in good yield and purity. The products have been characterized after purification by IR, 1H NMR, 13C NMR and MS. [Copyright &y& Elsevier]

A simple, highly sensitive, accurate and selective method for the determination of trace amounts of Ni2+ ions in water samples is proposed. The method is based on the separation and preconcentration of Ni2+ on an octadecyl-bonded silica (ODBS) membrane disk modified by a recently synthesized Schiff’s base N,N′-bis (3-methylsalicylidene) ortho phenylene diamine (MSOPD) at pH 7. The synthesis of this extractant ligand is also described. The retained nickel on the membrane was eluted with 2×5 ml 0.5 M HNO3 and measured by flame atomic absorption spectrometry (FAAS) at 232.0 nm. The extraction efficiency and the influence of the type and least amount of eluent for the stripping of Ni2+ from the disks, pH, flow rates of sample solution and eluent, amount of MSOPD, effect of other ions, and breakthrough volume were evaluated. The maximum capacity of the membrane disks modified by 3 mg of MSOPD was found to be 146±4 μg Ni2+. The 3σ limit of detection of the method was 30 ng per 1000 ml and also an enrichment factor of 250 was obtained. The proposed method has been applied to the determination of nickel in several water samples with satisfactory results. [Copyright &y& Elsevier]

Abstract: We present a novel, convenient, and efficient method for synthesizing polysubstituted 3-oxo-2,3-dihydro-5H-[1,3]thiazolo[3,2-a]pyrimidines via a three-component reaction. The zwitterions generated from the reaction of isocyanides and dialkyl acetylenedicarboxylates react with 2-imino-1,3-thiazolidin-4-one to produce the title compounds in good yields. [Copyright &y& Elsevier]

Abstract In this work, one-step synthesis of highly dispersible phthalocyanines containing carboxamide moieties via four-component Ugi reaction was demonstrated for the first time. These pseudopeptide-modified-phthalocyanines were characterized by means of IR, NMR, CHN and UV–Vis spectroscopy. Additionally, the purity of the pseudopeptide phthalocyanines was confirmed by capillary zone electrophoresis. Most of the synthesized phthalocyanines showed good dispersity in common organic solvents and especially in water. The in vitro photodynamic activities of water-soluble phthalocyanine 5k upon MCF-7 cancer cells were investigated and revealed that the cell viability was high in dark conditions, while the compound was phototoxic at visible light and the intensity of damage was directly related to its concentration. Also, phthalocyanine 5k showed high cellular uptake and more killing cells after the modification with Ugi-4CR. Since, many potent phthalocyanine photosensitizers are hydrophobic and poorly water-soluble, which limit their therapeutic applications, the novel phthalocyanines which modified through Ugi approach could be introduced as potent hydrophilic, nonaggregated and biocompatible sensitizers which can able to improve the effectiveness of photodynamic therapy. Graphical abstract One-step synthesis of highly dispersible phthalocyanines containing carboxamide moieties via four-component Ugi reaction as a potent photosensitizer was demonstrated for the first time. Image 1 Highlights • One-step synthesis of phthalocyanines containing carboxamide moieties Ugi four-component reaction was demonstrated. • Modified metallophthalocyanines showed high stability and dispersity in common solvents such as water. • Novel pseudopeptide-modified-phthalocyanines showed potential activity as a photosensitizer. [ABSTRACT FROM AUTHOR]

[Display omitted] • An on-chip electromembrane extraction was applied for copper measurement. • A customized Android app was designed based on the concepts of image analysis. • A QR code-based RGB analysis using a smartphone was developed. • The program has the ability to distinguish outlier colors. • Regression was done using weighted parameters of red (R), green (G), and blue (B). A miniaturized on-chip electromembrane extraction device with QR code-based red–green–blue analysis was designed to determine copper in water, food, and soil. The acceptor droplet consisted of ascorbic acid as the reducing agent and bathocuproine as the chromogenic reagent. The formation of a yellowish-orange complex was a sign of copper in the sample. Then, the qualitative and quantitative analysis of the dried acceptor droplet was done by the customized Android app that was developed based on image analysis concepts. In this application, principal component analysis was performed on the data for the first time to reduce the three dimensions, red, green, and blue, to one dimension. The effective extraction parameters were optimized. The limit of detection and limit of quantification were 0.1 µg mL−1. Intra- and inter-assay relative standard deviations ranged between 2.0 and 2.3 % and 3.1–3.7 %, respectively. The calibration range was studied between 0.1 and 25 µg mL−1 (R2 = 0.9814). [ABSTRACT FROM AUTHOR]

A fast and convenient protocol for the synthesis of novel spirooxindole derivatives in excellent yields was developed by the three-component reactions of malononitrile, isatin, and 2,3-dihydro-5 H -[1,3]thiazolo[3,2- a ]pyrimidine-5,7(6 H )-dione in the presence of diisopropylethylamine. [ABSTRACT FROM AUTHOR]

An efficient and facile one-pot synthesis is described for the preparation of novel tricyclic fused pyranothiazolopyrimidines containing both biologically active thiazolopyrimidine and pyranopyrimidine templates via three-component reaction involving an isocyanide with a dialkylacetylenedicarboxylate (DAAD) and 2,3-dihydro-5 H -[1,3]thiazolo[3,2- a ]pyrimidine-5,7(6 H )-dione, in high yields. [ABSTRACT FROM AUTHOR]

Abstract: Novel, one-pot, three-component reactions of the zwitterions generated in situ from pyridine and acetylenic esters with alkoxymethylenemalononitriles via 1,4-dipolar cycloadditions are described. The reactions afforded dialkyl 1,1-dicyano-2-alkoxy-1,9a-dihydro-2H-quinolizine-3,4-dicarboxylate derivatives in good to high yields without using any catalyst or activation. Structural, electronic, energetic, and mechanistic details of the reaction are also revealed by density functional theory (DFT) calculations, which strongly support the exclusive formation of the observed products. [Copyright &y& Elsevier]

Abstract: A new electrocatalyst, Au-SH-SiO2 nanoparticles immobilized on the metal-organic frameworks (MOFs) was synthesized and characterized by scanning electron microscopy (SEM), the transmission electron microscopy (TEM) and cyclic voltammetry (CV). The prepared electrocatalyst immobilized onto the surface of a glassy carbon electrode (GCE) to obtain Au-SH-SiO2@Cu-MOF/GCE. The sensor showed good electrocatalytic activity toward the oxidation of hydrazine in the neutral phosphate buffer solution (pH 7.0). The kinetic parameters such as the electron transfer coefficient (α) and the catalytic rate constant (k cat) for the oxidation of hydrazine were determined. The diffusion coefficient (D) of hydrazine in solution was also calculated by chronoamperometry. The potential application of the sensor was demonstrated by applying to the analytical determination of hydrazine concentration. Our results showed that the sensor had good electrocatalytic activity toward determination of hydrazine and exhibited a low detection limit (0.01μM), a wide linear range (0.04–500μM), and high sensitivity (0.1μAμM−1) as well as good stability and repeatability. The sensor has been successfully applied to determine hydrazine in water samples with good accuracy and precision. [Copyright &y& Elsevier]

Abstract: A novel atom economical diastereoselective synthesis of 5-iminooxazolines and their subsequent transformation to α,α-disubstituted dipeptide esters is described. Heating a mixture of cyclohexyl isocyanide and Z-α-benzoyl amino-acrylic acid alkyl esters under solvent-free conditions, afforded 5-iminooxazolines, which, upon specifications provided α,α-disubstituted dipeptide esters in good yield. [Copyright &y& Elsevier]