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Yavari, H. ,
Bakht, Bahareh Khojasteh ,
Zali boeini, H. ,
Torabi, M. ,
Shams Harandi M. ,
Shams solari, I. ,
Farahbakhsh, Z. ,
Varma, R.S. Sensors and Actuators B: Chemical (09254005) 379
A reversible multichannel chemosensor IPBTO [E)-5-(4-(1H-imidazo[4,5-b]phenazin-2-yl) benzylidene)-2-thioxothiazolidin-4-one] was fabricated as a D-pi-A system and used for the detection of cyanide ion (CN-) in aqueous solutions. This chemosensor exhibited a switch-off fluorescence response at 566 nm for CN- in the presence of other tested anions. The detection limit of IPBTO toward CN- was 0.7 mu M with the association constant being 2.0 x 106 M-1. The reversibility and reusability aspects of this chemosensor were investigated for five consecutive runs, and good results were obtained. In addition, IPBTO as a bioimaging agent with good cell viability was deployed for the detection of CN- in MDA-MB-231 cells. Excellent potential for sensing CN- was also realized for this chemosensor in food and environmental samples. Besides, IPBTO was self-assembled on the gold electrode surface (Au-IPBTO SAM) and used for accumulation and detection of CN- in aqueous media. This modified electrode was characterized by ATR surface analysis, and the electrochemical behavior of the electrode was studied utilizing cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). Our results have conclusively revealed that this electrochemical sensor could be successfully used to detect CN-.
Separation and Purification Technology (13835866)
An extraction-electrooxidation (E-EODS) system is introduced for the removal of dibenzothiophene (DBT) from model fuel (DBT in n-hexane). The process is run in an electrochemical cell as a batch reactor, where, the model fuel is in contact with an appropriate immiscible polar solvent composed of acetonitrile and water (MeCN-water, 90:10% v/v) that serves as both the extraction solvent and electrochemical medium. The electrochemical oxidation of DBT, which is extracted into the MeCN-water phase, enhances the continuous removal of DBT from the model fuel phase. The effects of the composition of the extraction solvent, applied potential and the process time on DBT removal efficiency are assessed. The results indicate that with the selection of the MeCN-water, 90:10 v/v in a 1:1 ratio respect to the model fuel, this extraction method yields about 100% extraction efficiency within 5 h, at 25 °C at 2.9 V and atmospheric pressure as determined by HPLC technique. Cyclic voltammetry (CV), Fourier transform infrared (FT-IR) spectroscopy, and gas chromatography-mass spectrometry (GC–MS) techniques are applied to identify the electrochemical oxidation products of DBT. The electrochemical oxidation-derived extraction process through this method is innovative and feasible for deep desulfurization of liquid fossil fuels. © 2021
International Journal of Hydrogen Energy (03603199) (1)
The glassy carbon electrode is modified by poly(brilliant cresyl blue) (PBCB) to be applied as a new green and efficient platform for Pt and Pt–Ru alloy nanoparticles deposition. Surface composition, morphology and catalytic activity of these modified electrodes towards methanol oxidation are assessed by applying X-ray diffraction, field emission scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy techniques. The X-ray diffraction patterns reveal that the highly crystalline Pt and Pt–Ru alloy and RuO2 nanoparticles with low crystallinity are deposited on the PBCB modified glassy carbon electrodes. The microscopic images indicate smaller size and better distribution of deposited nanoparticles on the surface of PBCB modified electrodes. Cyclic voltammetry and electrochemical impedance spectroscopy results reveal that PBCB supported Pt and Pt–Ru nanoparticles have better electrocatalytic performance and durability towards methanol oxidation rather than the unsupported nanoparticles. From the obtained results it can be concluded that the presence of PBCB not only improves the stability of nanoparticles on the surface, but also leads to the formation of smaller size and more uniform distribution of nanoparticles on the surface, which, in turn, cause the nanoparticles to provide a higher accessible surface area and more active centers for the oxidation of methanol. The results will be valuable in extending the applications of this polymer in surface modification steps and in developing promising catalyst supports to be applied in direct methanol fuel cells. © 2019 Hydrogen Energy Publications LLC
Chemical Engineering Journal (13858947)
Environmental-friendly waterborne polyurethane/graphene oxides nanocomposites (WPU/GOs) were prepared using p-tert-butyl calix[4]arene (BC4A) and sodium p-sulfonatocalix[4]arene (SC4A) modified GO nanosheets (CGO and SGO) as novel anti-corrosion coatings. Structural, thermal, and morphological investigation of nanosheets by FTIR, XRD, Raman, XPS, TGA, and SEM analysis confirmed their synthesis successfully. Moreover, different properties of WPU/GOs films were also evaluated by ATR-FTIR, XRD, SEM, contact angle, TGA, DSC and tensile analysis. It was found that the modification of GO nanosheets with BC4A and SC4A macrocycles not only overcome the flocculation and coagulation problem of unmodified GO incorporated WPU dispersion (WPU/GO) but also afford better mechanical properties to nanocomposites. The SEM morphological inspection exhibited that the microphase separation degree and dispersion quality of nanosheets within the nanocomposites strongly depends on the type of incorporated nanosheets. Regarding WPU/CGO and WPU/SGO nanocomposites, CGO and SGO nanosheets provide the enhanced storage stability and dispersibility compared to unmodified GO in WPU/GO sample. Anti-corrosion efficiency of the samples was also evaluated by PDS and EIS techniques and the results revealed that the WPU/CGO sample acts as a highly efficient anti-corrosion coating for mild steel and can be introduced as green corrosion protective coating with inhibition efficiency of 99.8%. © 2018 Elsevier B.V.
Colloids and Surfaces B: Biointerfaces (09277765) 165pp. 135-143
Nickel-cysteine nanostructures (Ni-CysNSs) are prepared by a simple wet chemistry procedure under mild conditions, in which L-cysteine acts both as precursor and structure directing agent. This method involves the reaction of nickel chloride with L-cysteine, followed by simultaneous adjusting the pH in the range of 6–8.5 by addition of an aqueous NaOH solution. The structure and morphology of the prepared products are characterized using various techniques, including X-ray powder diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, CHNS elemental analysis, Field emission scanning electron microscopy (FESEM) and Transmission electron microscopy (TEM). The effects of a variety of synthetic conditions on the structure and morphology of the Ni-CysNSs are studied, including the molar ratio of precursors, dispersing solvent, pH value of the reaction solution, reaction time and reaction temperature. FT-IR measurements reveal that synthesized Ni-CysNSs contain many free carboxylic groups on the surface, which could be used as binding sites to anchor biological molecules in order to develop various bioelectronic devices. In this work, the applicability of synthesized nanostructure in biosensing is studied by using Ni-CysNSs as a platform for covalently immobilization of GOx, as a model enzyme, on the surface. Cyclic voltammetric measurements reveal that the direct electron transfer from the active center of GOx to the glassy carbon electrode facilitated upon its immobilization on the Ni-CysNSs film. More importantly, GOx preserves its native structure and catalytic activity for the oxidation of glucose after immobilization on the Ni-CysNSs surface. The electrocatalytic characteristics of the GC/NiCysNS/GOx electrode toward the oxidation of glucose are investigated by cyclic voltammetry, which displayed acceptable electrical and sensing performance. Simple preparation of Ni-CysNPs and their biocompatibility make them attractive platforms for integration of various biomolecules such as proteine/enzymes with surface. © 2018
Journal of Electroanalytical Chemistry (15726657)
In this paper, simple strategies for the modification of glassy carbon electrode (GCE) with iron-4″(phenyl)-2, 2″:6″, 2“-terpyridine complex (Fe-PTPY) and Fe-PTPY covalently bonded to ordered mesoporous carbon (OMC) are described. The Fe-PTPY/OMC modified GCE (Fe-PTPY/OMC/GCE) was prepared in a three steps strategy. In the first step, OMC modified GCE was prepared by simple casting. Then, PTPY ligand was attached directly to the electrode surface through electrochemical reduction of 4'(4aminophenyl)-2, 2':6', 2“-terpyridine (APTPY) diazonium salt. The modification was completed by iron attachment to the electrode surface through complex formation reaction with surface PTPY groups. The Fe-PTPY modified GCE (Fe-PTPY/GCE) was prepared in similar manner by omitting the first step of the above strategy. The reactions progress and the electrochemical behavior of the modified electrodes were studied using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The modified electrodes showed good electrocatalytic activity for reduction of H2O2. Using hydrodynamic amperometry, under optimum conditions, calibration plots for H2O2 were linear in the ranges of 0.15–0.4 and 0.4–5.0 mM with slopes of 0.2743 and 0.2112 μA/mM on Fe-PTPY/GCE and 0.01–0.1 and 0.1–13.0 mM with slopes of 4.91 and 0.91 μA/mM on Fe-PTPY/OMC/GCE, respectively. © 2017 Elsevier B.V.
Journal of Solid State Electrochemistry (14328488) (2)
In this study, a new procedure for the fabrication of biosensors was developed. The method is based on the covalent attachment of nitrophenyl groups to the electrode surface via diazonium salt reaction followed by their conversion to amine moieties through electrochemical reduction and electrostatic layer-by-layer (LbL) assembly technique. In this procedure, highly stable iron oxide (Fe3O4) nanoparticles (IONPs), chitosan (CHIt), GOx, and Nile blue (NB) were assembled on the surface of aminophenyl modified glassy carbon electrode (AP/GCE) by LbL assembly technique. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to characterize the interfaces. The surface coverage of the active GOx and Michaelis–Menten constant (KM) of the immobilized GOx were Γ = 3.38 × 10−11 mol cm−2 and 2.54 mM, respectively. The developed biosensor displayed a well-defined amperometric response for glucose determination with high sensitivity (8.07 μA mM−1) and low limit of detection (LOD) of 19.0 μM. The proposed approach allows simple biointerface regeneration by increasing pH which causes disruption of the ionic interactions and release of the electrostatic attached layers. The biosensor can then be reconstructed again using fresh enzyme. Simple preparation, good chemical and mechanical stabilities, and easy surface renewal are remarkable advantages of the proposed biosensor fabrication procedure. © 2015, Springer-Verlag Berlin Heidelberg.
Fullerenes Nanotubes and Carbon Nanostructures (1536383X) (12)
In this work, a functionalized mesoporous carbon (CMK-3-O) was synthesized after oxidation with nitric acid and was used to adsorb dibenzothiophene (DBT) from model oil for the first time. Then, its performance was compared with that of CMK-3. The functionalized mesoporous carbon, CMK-3-O, showed better a capacitance performance for DBT adsorption than that of CMK-3. The maximum adsorption capacity was obtained for functionalized mesoporous carbon at optimum conditions with 6 M HNO3 aqueous solution and 30 min contact time. The physical and structural properties of CMK-3-O and CMK-3 were investigated with X-ray diffraction method (XRD), N2 adsorption–desorption isotherm, FT-IR, and elemental analysis (CHNO). Results of the elemental analysis showed that the oxygen and nitrogen content has increased and the carbon content has decreased through oxidation treatment. The effects of various factors on the adsorption process (such as temperature, amount of adsorbent, contact time, and concentration) of DBT were studied. CMK-3-O showed a maximum adsorption capacity of 86.96 mg DBT g−1 of CMK-3-O at optimized conditions (temperature, 25°C; adsorbent dosage, 20 g L−1; contact time, 60 min), which was a higher adsorption capacity of that observed for CMK-3 (57.47 mg DBT g−1 of CMK-3). Kinetic studies have revealed that the adsorption of DBT can be described by a pseudo-second-order rate equation. Equilibrium data showed that adsorption process was best represented by the Langmuir model. The results also illustrated the fact that the regenerated adsorbent afforded 64.3% of the initial adsorption capacity after the two regeneration cycles. © 2016 Taylor & Francis Group, LLC.
Journal of Electroanalytical Chemistry (15726657)
In this paper, a new methodology is developed for the modification of glassy carbon electrode (GCE) with covalently modified ordered mesoporous carbon (OMC) with glucose oxidase (GOD) as a model of electroactive biomolecules. In this methodology the following steps were followed: (1) preparing the OMC modified GCE (OMC/GCE) by simple casting, (2) functionalization of OMC/GCE with 4-nitrophenyl (NP) group by electrochemical reduction of 4-nitrobenzenediazonium salt in nonaqueous media, (3) converting the surface NP to aminophenyl (AP) through electrochemical reduction, (4) covalent attachment of 2,4,6-trichloro-1,3,5-triazine (TCT) to the surface of electrode through its reaction with AP and (5) enzyme immobilization through reaction between GOD and surface TCTs. The direct electrochemistry and catalytic activity of the immobilized GOD on OMC are investigated. Although the cyclic voltammetry (CV) revealed direct electron transfer (DET) between GOD and the OMC modified electrode, however, the biosensor shows response to glucose only in the presence of oxygen, indicating the DET capability and enzymatic activity occurred on different immobilized GODs. The surface coverage of GOD with DET property and GOD with enzymatic activity are 2.94 × 10-10 and 6.87 × 10-12 mol cm-2, respectively. The obtained glucose biosensor shows excellent analytical performance for glucose determination. © 2015 Elsevier B.V. All rights reserved.
Journal of Magnetism and Magnetic Materials (03048853)
In this work, magnetic ordered mesoporous carbon adsorbent was synthesized using soft templating method to adsorb sulfur from model oil (dibenzothiophene in n-hexane). Through this research, pluronic F-127, resorcinol-formaldehyde and hydrated iron nitrate were respectively used as soft template, carbon source and iron source. The adsorbent was characterized by X-ray diffraction, nitrogen adsorption-desorption isotherm and transmission electron microscopy. Nitrogen adsorption-desorption measurement revealed the high surface area (810 m2 g-1), maxima pore size of 3.3 nm and large pore volume (1.01 cm3 g-1) of the synthesized sample. The adsorbent showed a maximum adsorption capacity of 111 mg dibenzothiophene g-1 of adsorbent. Sorption process was described by the pseudo-second-order rate equation and could be better fitted by the Freundlich model, showing the heterogeneous feature of the adsorption process. In addition, the adsorption capacity of regenerated adsorbent was 78.6% of the initial level, after five regeneration cycles. © 2015 Elsevier B.V. All rights reserved.
Petroleum Science and Technology (10916466) (13)
The extractive desulfurization of a model and several real gasoline samples was investigated using imidazolium-based ionic liquids (ILs). Factorial design of experiments indicated that, among several process variables, the number of extraction steps and the IL/gasoline volume ratio were statistically highly significant. The results showed a desulfurization efficiency of 95.2% under the optimal conditions. The following order was observed for the extraction of thiophenic compounds: benzothiophene>thiophene>3-methylthiophene>2- methylthiophene, with 96.1% removal efficiency for the first one. The IL extraction was applied as a complementary process for the oxidative desulfurization by hydrogen peroxide and formic acid, which provided high efficiency and selectivity for desulfurization of gasoline. Copyright © 2014 Taylor & Francis Group, LLC.
Biosensors and Bioelectronics (18734235) 56pp. 313-319
Herein we describe improved electron transfer properties and catalytic activity of nickel oxide nanoparticles (NiONPs) via the electrochemical deposition on DNA modified glassy carbon electrode (DNA/GCE) surface. NiONPs deposited on the bare and DNA-coated GCE showed different morphologies, electrochemical kinetics and catalytic activities. The atomic force microscopy (AFM) images revealed the formation of triangular NPs on the DNA/GCE that followed the shape produced by the DNA template, while the electrodeposition of NiONPs on the bare GCE surface led to the formation of spherical nanoparticles. Electrochemical impedance spectroscopy (EIS) measurements revealed lower charge-transfer resistance (Rct) of triangular NiONPs compared to spherical NPs. Furthermore, the electrocatalytic activity of triangular NiONPs compared to spherical NPs toward glucose oxidation in alkaline media was significantly improved. The amperometric oxidation of glucose at NiONP-DNA/GCE, yielded a very high sensitivity of 17.32mAmM-1cm-2 and an unprecedented detection limit of 17nM. The enhanced electron transfer properties and electrocatalytic activity of NiONP-DNA/GCE can be attributed to the higher fraction of sharp corners and edges present in the triangular NiONPs compared to the spherical NPs. The developed sensor was successfully applied to the determination of glucose in serum samples. © 2014 Elsevier B.V.
Microporous and Mesoporous Materials (13871811)
In this study, a mesoporous carbon with large surface area (CMK-5) was studied for the first time for adsorption of dibenzothiophene (DBT) as a model sulfur compound, and its performance was compared with that of CMK-3. The mesoporous carbon was synthesized from mesoporous silica SBA-15 as the hard template and furfuryl alcohol as the carbon source. The structural and textural properties of the synthesized samples were characterized by means of X-ray diffraction, transmission electron microscopy and nitrogen adsorption-desorption techniques. The CMK-5 afforded a maximum adsorption capacity of 125 mg DBT g-1 of the adsorbent at the optimized conditions (adsorbent dose, 2 g L-1; contact time, 1 h; temperature, 25°C), which was twice of that observed for CMK-3 (62.5 mg DBT g-1). The higher adsorption capacity of CMK-5 compared to CMK-3 is ascribed to its unique structure composed of ordered arrays of carbon nanopipes separated by ordered arrays of mesoporous channels in a bimodal pore system. Kinetic studies revealed that the sorption process achieved equilibrium within 60 min and followed a pseudo-second-order rate equation. Langmuir isotherm best represented the equilibrium adsorption of DBT onto CMK-5. The negative value of Gibbs free energy (-15.3 kJ mol -1) for CMK-5 indicated that the adsorption occurs via a spontaneous process. The CMK-5 adsorbent could be easily regenerated by washing with toluene. The regenerated adsorbent afforded 86.3%, and 86.0% of the initial adsorption capacity after the first two regeneration cycles, respectively. The corresponding values for CMK-3 were 76.9% and 75.2%. © 2012 Elsevier Inc. All rights reserved.
Journal of Electroanalytical Chemistry (15726657)
We describe here the covalent modification of glassy carbon electrode with nile blue (NB), a redox dye, by electrochemical reduction of its corresponding diazonium salt, which is generated in situ from the reaction between the aromatic amino phenyl group of NB and sodium nitrite. NB is attached directly to the electrode surface without any cross linking agent or complex matrices. This modification method is very rapid, simple, in one step and provides a very stable grafted NB film. Cyclic voltammetry and electrochemical impedance spectroscopy were used to trace the reaction. The resulting NB films have a very stable and reversible electrochemical response and exhibit excellent electrocatalytic behavior toward hydrogen peroxide and oxygen reduction. The amperometric detection of hydrogen peroxide is performed at -0.15 V vs. Ag/AgCl. This strong catalytic effect for reduction of hydrogen peroxide and oxygen exhibited a biocompatible platform for development of glucose biosensors. Therefore, a glucose biosensor is developed using glucose oxidase by simple casting method based on decreasing of cathodic peak current of oxygen. This biosensor has been successfully applied to determination of glucose in human plasma sample. The great stability and reusability, excellent electrochemical reversibility, technically simple and possibility of preparation at short period of time make this method suitable for low-cost bioelectronical devices. © 2013 Elsevier Ltd. All rights reserved.
Electrochimica Acta (00134686)
This study reports a novel, simple and fast approach for construction of a highly stable glucose biosensor based on the immobilization of glucose oxidase (GOx) onto a glassy carbon electrode (GCE) electrografted with 4-aminophenyl (AP) by diazonium chemistry. Aminophenyl was used as cross-linker for covalent attachment of glucose oxidase to the electrode surface. Cyclic voltammograms of the GOx-modified GCE in phosphate buffer solution exhibited a pair of well-defined redox peaks, attesting the direct electron transfer (DET) of GOx with the underlying electrode. The proposed biosensor could be used to detect glucose based on the consumption of O2 with the oxidation of glucose catalyzed by GOx and exhibited a wide linear range of glucose from 0.05 mM to 4.5 mM and low detection limit of 10 μM. The surface coverage of active GOx, heterogeneous electron transfer rate constant (ks) and Michaelis-Menten constant (KM) of immobilized GOx were 1.23 × 10-12 mol cm-2, 4.25 s-1 and 2.95 mM, respectively. The great stability of this biosensor, technically simple and possibility of preparation at short period of time make this method suitable for fabrication of low-cost glucose biosensors. © 2013 Elsevier Ltd. All rights reserved.
Journal of Electroanalytical Chemistry (15726657)
In this work, a new organic-inorganic hybrid compound containing N,N′-bis(salicylidene)-1,2-phenylenediaminocobalt (III) (CoSal) complex and a Keggin type polyoxometalate, H4SiW12O40 (SiW12), has been synthesized and characterized. FT-IR spectra showed the presence of both species, UV/Vis spectra displayed the interaction between CoSal and POM in the hybrid compound and XPS determined the oxidation states of cobalt in CoSal and in the hybrid compound. Elemental (CHN) and thermogravimetry analyses showed that 4 mol of CoSal complex react with one mole of SiW 12 to form (CoSal)4SiW12. This compound was used as a bulk-modifier to fabricate the chemically modified carbon paste electrode (CPE) by direct mixing. The electrochemical behavior and electrocatalysis of bulk modified CPE was studied in 1MH2SO 4 acidic solution by cyclic voltammetry in detail. The results indicate that the modified electrode has a notable bifunctional catalytic activity. It reduces iodate and this property is attributed to the function of SiW12; on the other hand, it oxidizes cysteine due to the function of the CoSal complex. Analytical features of the sensor for amperometric determination of iodate and cysteine were also evaluated. The sensor has a good stability; moreover, it can be renewed easily and repeatedly through a mechanical polishing process. These properties make the modified CPE a good candidate to act as a bifunctional electrocatalyst and an electrochemical sensor as well. © 2013 Elsevier Ltd.
Electroanalysis (10400397) (8)
We describe here the covalent modification of a glassy carbon electrode with toluidine blue (TB) diazonium salt, which is generated in situ from the reaction between the aromatic amino phenyl group of TB and sodium nitrite. TB is attached directly to the electrode surface without any cross-linking agent or complex matrices. The resulting TB films exhibit excellent electrocatalytic behavior toward NADH oxidation. Low potential detection of NADH is performed at 0.15V vs. Ag/AgCl. Furthermore, an ethanol biosensor is developed using the TB modified electrode and alcohol dehydrogenase. The great stability and reusability, excellent electrochemical reversibility, technically simple preparation and short preparation time make this method suitable for low-cost bioelectronical devices. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Biosensors and Bioelectronics (18734235) (1)
The glassy carbon (GC) electrode modified by nickel oxide nanoparticles (NiOxNPs) is proposed as a novel electrocatalytic system for the oxidation of NADH without using any electron transfer mediator. Here, chronoamperometry was used not only as a simple method for the deposition of NiOxNPs onto the GC electrode but also as an efficient tool in the controlling of nanoparticles size and efficient electrocatalytic activity. The surface morphology and electrochemical properties of the NiOxNPs/GC electrode was investigated using scanning electron microscopy and cyclic voltammetry techniques, respectively. The NPs are deposited uniformly across the GC surface and the size of NiOxNPs varies from 20 to less than 100nm. The NiOxNPs/GC electrode shows excellent electrocatalytic activity toward oxidation of NADH at reduced overvoltage. The detection limit and sensitivity of the modified electrode toward NADH were estimated to be 106nM (S/N=3) and 0.052μAμM-1, respectively at a concentration range up to 1mM. Due to the biocompatibility of NiOxNPs toward biomolecules, this modified electrode can be used as an efficient transducer in the design of an ethanol biosensor based on the coupled alcohol dehydrogenase enzyme(ADH). Hydrodynamic amperometric detection of ethanol on the ADH-Nafion/NiOxNPs/GC modified electrode gives linear responses over the concentration range of 0.2-6mM with a detection limit of 6.4μM and sensitivity of 36nAmM-1. Applicability of the proposed biosensor for ethanol detection in real samples, easy and simple preparation, being mediator free, high sensitivity and biocompatibility are the major advantages of the proposed biosensor. © 2013 Elsevier B.V.
Electroanalysis (10400397) (9)
In the present study, a novel mixture consisting of N,N'-bis(salicylidene)-1,2-phenylenediamino cobalt (CoSalophen, CoSal) complex and (n-butyl)4SiW12O40 (SiW12), have been used to chemically modify a carbon paste electrode (CPE) for sensitive determination of cysteine (CySH). The electrocatalytic effect of the newly developed modified CPE towards oxidation of CySH was evaluated by comparing cyclic and differential pulse voltammograms in the presence of cysteine at bare, CoSal, SiW12 and CoSal/SiW12 modified CPE. The differential pulse voltammetry method was applied as a sensitive method for quantitative detection of CySH trace amounts, the experimental conditions being optimized in order to evaluate the best analytical parameters of the sensor. Reproducibility and stability studies were also performed and the sensor was applied for the determination of CySH in a pharmaceutical sample and in human blood serum and urine samples. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Journal of Electroanalytical Chemistry (15726657)
In this study, a new inorganic-organic hybrid compound consisting of a Keggin type polyoxometalate, H4SiW12O40 (SiW12), and Nile blue (NB) was synthesized and characterized. The (NB)2H2SiW12O40 (NB 2SiW12) hybrid compound was characterized by Fourier transform infrared (FT-IR), elemental (CHNS) analysis, UV-Vis and thermogravimetry techniques, and used as a bulk modifier to fabricate a chemically modified carbon paste electrode (CPE) by direct mixing. The electrochemical behavior of the newly NB2SiW12 composite CPE was analyzed by cyclic voltammetry, and the electrode was applied for nitrite reduction, exhibiting high electrocatalytic activity. Determination of nitrite by fixed potential amperometry was done under various experimental conditions and, at the optimum conditions, the linear response ranged from 5 to 1200 μM with a high sensitivity of and a low detection limit. The electrode has the remarkable advantage of surface renewal owing to bulk modification, as well as simple preparation, good mechanical and chemical stability and reproducibility. No noticeable interferences from other ionic species usually found in natural water were observed. The new developed electrode has been successfully applied for detection of nitrite in real water samples. © 2013 Published by Elsevier B.V.
Analytical Methods (17599679) (5)
New enzyme biosensors for cholesterol detection based on a recently developed transduction platform constituted of a GCE modified with polymer redox mediator poly(methylene blue) (PMB) and conducting polymer poly(3,4- ethylenedioxythiophene) (PEDOT) were for the first time prepared and evaluated. The enzyme cholesterol oxidase (ChOx) was immobilized by simple adsorption, the ChOx/PEDOT/PMB/GCE biosensor being applied for amperometric determination of cholesterol by monitoring the peroxide reduction produced by the enzymatic reaction at -0.4 V vs. SCE. Amperometric studies at fixed potential reveal that almost interference-free cholesterol determination can be achieved at the newly developed biosensor in a range between 10 and 220 μM with a sensitivity of 79.0 μA cm-2 mM-1 and a detection limit of 1.6 μM. The recovery and storage stability of the biosensor were evaluated and the biosensor was applied to cholesterol detection in whole cow milk and chicken egg yolk. © 2013 The Royal Society of Chemistry.
Electroanalysis (10400397) (1)
A novel modified electrode with a conducting film containing poly(3,4-ethylenedioxythiophene) (PEDOT) plus poly(methylene blue) (PMB) on a glassy carbon electrode (GCE) (PEDOT/PMB/GCE) has been developed, and application illustrated as electrochemical sensor for ascorbate and biosensor for glucose. Electrocatalytic oxidation at 0.0V vs. SCE was successfully used for the determination of ascorbate in real samples. Glucose biosensors containing glucose oxidase (GOx) immobilized on PMB/PEDOT electrodes exhibit enhanced sensitivity relative to PEDOT ones. The new robust biosensor architecture shows a far superior operational and storage stability relative to PMB alone, enabling excellent preservation of enzyme activity during more than one month. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Tetrahedron Letters (18733581) (35)
Moisture and air-stable, robust palladacycle phosphine-ylide complexes as catalyst precursors were used in additive- and amine-free Sonogashira cross-coupling reactions. Various aryl halides were coupled with phenylacetylene in DMF, under air, in the presence of 0.001 mol % of the catalyst to afford the corresponding cross-coupled products in good to excellent yields. Application of the five-membered palladacycle [(P^C)PdCl2] (C1) in Sonogashira coupling reaction produced comparable catalytic activities of the seven-membered [(C^C)PdCl2] (C2) analogs. © 2013 Elsevier Ltd. All rights reserved.
Journal of the Iranian Chemical Society (17352428) (2)
The use of iron oxide/amino-functionalized silica core-shell magnetic nanoparticles for preconcentration of Pb2+ followed by its consecutive atomic absorption spectrometry determination is described. Effects of various operating variables, namely, solution pH, initial Pb2+ concentration, contact time, adsorbent dosage, sample volume, concentration and volume of desorbing solution, and co-existing ions on solid-phase extraction (SPE) of Pb2+ were studied by batch equilibrium technique. The experimental adsorption data were well fitted to the Langmuir isotherm model. The Langmuir adsorption capacity and equilibrium time were found to be 100 mg g-1 and 20 min, respectively. The adsorption data were also fitted to kinetic pseudo-first-order and pseudo-second-order models. Kinetic studies showed that the adsorption followed pseudo-second-order model. Under the optimal SPE conditions, the enrichment factor, detection limit and relative standard deviation for determination of Pb2+ were found to be 211, 1 μg L-1, and 3.7 % for 50 μg L-1, respectively. The proposed method was successfully applied to the determination of lead in a real sample with satisfactory results. © 2012 Iranian Chemical Society.
Journal of Chemistry (20909071)
Magnetite silica core-shell nanoparticles (FeSiO were synthesized and evaluated as a nanoadsorbent for removing Zn(II) from aqueous solutions. The core-shell nanoparticles were prepared by combining coprecipitation and sol-gel methods. Nanoparticles were characterized by X-ray diffraction, transmission electron microscopy (TEM), and FT-IR. The magnetization values of nanoparticles were measured with vibrating sample magnetometer (VSM). The adsorption of Zn(II) ions was examined by batch equilibrium technique. The effects of pH, initial Zn(II) concentration, and contact time on the efficiency of Zn(II) removal were studied. The equilibrium data, analyzed by using Langmuir and Freundlich isotherm models, showed better agreement with the former model. Using the Langmuir isotherm model, maximum capacity of the nanoadsorbent for Zn(II) was found to be 119 mg g -1 at room temperature. Kinetic studies were conducted and the resulting data were analyzed using first- and second-order equations; pseudo-second-order kinetic equation was found to provide the best correlation. The adsorption and sedimentation times were very low. The nanoadsorbent can be easily separated from aqueous solution by a magnet. Repeated adsorption acid regeneration cycles were performed to examine the stability and reusability of the nanoadsorbent. The result of this study proved high stability and reusability of FeSiOas an adsorbent for Zn(II) ions. © 2013 Masoomeh Emadi et al.
Fuel Processing Technology (03783820)
We synthesized magnetic mesoporous carbon (Ni-CMK-3) as an adsorbent for removal of sulfur from model oil (dibenzothiophene, DBT, in n-hexane). X-ray diffraction and transmission electron microscopy analyses revealed the presence of face-centered cubic Ni nanoparticles with an average size of 17 ± 3 nm, and indicated that the carbon support retained its mesoporosity and morphology after immobilization of the metal nanoparticles. Nitrogen adsorption measurements indicated that the resultant Ni-CMK-3 possesses high surface area (705 m2 g- 1), large pore-volume (0.87 cm3 g- 1) and average pore-size of 4.5 nm. The resulting magnetic mesoporous carbon afforded a maximum adsorption capacity of 62.0 mg DBT g - 1 of Ni-CMK-3 at the optimized conditions (Ni loading, 20%; adsorbent dose, 5 g L- 1; contact time, 1 h; temperature, 40°C). Magnetic measurement revealed the ferromagnetic property of Ni-CMK-3 at room temperature with saturation magnetization, remanent magnetization and coercive force of 13.8 emu g- 1, 38.0 Oe and 2.2 emu g- 1, respectively, which made it desirable for separation under an external magnetic field. Following adsorption of DBT, Ni-CMK-3 could be separated by a magnet and regenerated by extraction with toluene. The regenerated adsorbent afforded 97%, 94% and 80% of the initial adsorption capacity after the first three regeneration cycles, respectively. © 2012 Elsevier B.V.
Comptes Rendus Chimie (16310748) (2)
The non-symmetric phosphorus ylides and their Pd(II) complexes have been synthesized as potential antioxidant and antibacterial compounds and their structures were elucidated using a variety of physicochemical techniques. The reaction of 1 equiv non-symmetric phosphorus ylides, Ph2PCH 2PPh2C(H)C(O)PhX (X = Br (Y1), Cl (Y 2), NO2 (Y3), OCH3 (Y4)) with [Pd(dppe)Cl2] (M1), followed by treatment with 2 equiv AgOTf led to monomeric chelate complexes, [(dppe)Pd(Ph2PCH 2PPh2C(H)C(O)PhX)] (OSO2CF3) 2 (X = Br (C1), Cl (C2), NO2 (C 3), OCH3 (C4)), which contain a five-membered P,P chelate ring in one side and a five-membered P,C chelate ring in the other side. Palladium ion complexes were synthesized and investigated by cyclic voltammetry, FT-IR, UV-visible, multinuclear (1H, 31P and 19F) NMR, thermal analysis and ESI-mass spectroscopic studies. Some complexes and ligands have been studied by powder XRD and single crystal X-ray diffraction techniques. FT-IR and 31P NMR studies revealed that the ylides Y are coordinated to the metal ions via the terminal phosphorus (P c) of the ylides and methene group (CH). The proposed coordination geometry around the Pd atom in these complexes is defined as slightly distorted square planar by UV-Visible and DFT studies. Thermal stability of all complexes was also shown by TG/DTG methods. Furthermore, the electrochemical behavior of the complexes was investigated by cyclic voltammetry. The results indicate that all complexes are successfully synthesized from the initial ligands. All complexes were analyzed for their antioxidant properties by DPPH free radical scavenging assay. In addition, the antibacterial effects of the hexane-solved complexes were investigated by disc diffusion method against four Gram positive and negative bacteria. All complexes represented antibacterial activity against bacteria tested especially on Gram positive ones. A theoretical study on the structure, 1H and 31P NMR chemical shifts and the interaction energy between the Pd2+ ion and ligands dppe and ylide Y is also reported. © 2012 Académie des sciences.
Petroleum Science and Technology (15322459) (15)
The authors report that 1-octyl-3-methylimidazolium tetrafluoroborate, [OMIM][BF 4], and 1-butyl-3-methylimidazolium hexafluorophosphate, [BMIM][PF 6], ionic liquids were synthesized and tested for their capability to desulfurization from model of gasoline. The results show that the aromatic sulfur compounds with higher π-electron density were favorably adsorbed. The results also show that [BF 4] --based ionic liquid displays higher extraction efficiencies than [PF 6] --based ionic liquid. Thus, it was shown that the extractive ability of the imidazolium ionic liquids was dominated by the structure of cation and anion. It is also found that the sizes of ionic liquids are important factors affecting the absorption capacity for aromatic sulfur compounds. © 2012 Taylor & Francis Group, LLC.
Synthetic Metals (03796779) (23-24)
Poly(3,4-ethylenedioxythiophene) (PEDOT) films have been formed by electropolymerization for the first time on top of poly(methylene blue) (PMB) modified GCE (PMB/GCE), in order to improve PMB modified electrode stability. Experimental conditions, such as electrolyte and fixed potential or potential cycling electrosynthesis have been optimized for PEDOT polymerization on bare GCE. Characterization of PMB modified together with PEDOT/PMB modified and bare GCE was done by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The operational and storage stability of PEDOT/PMB/GCE was tested. Its good stability and the lack of influence of dissolved oxygen on its electrochemical properties, make it promising for sensor and biosensor applications. © 2011 Elsevier B.V. All rights reserved.
Bioelectrochemistry (1878562X)
The modification of glassy carbon (GC) electrode with electrodeposited nickel oxide nanoparticles (NiOxNPs) and deoxyribonucleic acid (DNA) is utilized as a new efficient platform for entrapment of osmium (III) complex. Surface morphology and electrochemical properties of the prepared nanocomposite modified electrode (GC/DNA/NiOxNPs/Os(III)-complex) were investigated by FESEM, cyclic voltammetry and electrochemical impedance spectroscopy techniques. Cyclic voltammetric results indicated the excellent electrocatalytic activity of the resulting electrode toward oxidation of l-cysteine (CySH) at reduced overpotential (0.1V vs. Ag/AgCl). Using chronoamperometry to CySH detection, the sensitivity and detection limit of the biosensor are obtained as 44μAmM -1 and 0.07μM with a concentration range up to 1000μM. The electrocatalytic activity of the modified electrode not only for oxidation of low molecular-mass biothiols derivatives such as, glutathione, l-cystine, l-methionine and electroactive biological species ( dopamine, uric acid, glucose) is negligible but also for very similar biothiol compound (homocysteine) no recognizable response is observed at the applied potential window. Furthermore, the simultaneous voltammetric determination of l-cysteine and homocysteine compounds without any separation or pretreatment process was reported for the first time in this work. Finally, the applicability of sensor for the analysis of CySH concentration in complex serum samples was successfully demonstrated. Highly selectivity, excellent electrocatalytic activity and stability, remarkable antifouling property toward thiols and their oxidation products, as well as the ability for simultaneous detection of l-cysteine and homocysteine are remarkably advantageous of the proposed DNA based biosensor. © 2012 Elsevier B.V.
Chemical Engineering Journal (13858947)
In the study, porcine pancrease lipase (PPL) was covalently immobilized on the surface of silica-coated modified magnetite nanoparticles. The synthesis process consists of the following steps: (1) preparing magnetic iron oxide nanoparticles using the co-precipitation method, (2) coating NP with silica (SiO 2) by sol-gel reaction, (3) preparing amino-functionalized magnetite NPs by treating silica-coated NPs with 3-aminopropyltriethoxysilane, (4) activating immobilization of PPL on the activated amino- functionalized magnetite NPs, and (5) covalently immobilization of PPL on the activated- amino- functionalized magnetite NPs. The synthesis steps and characterizations of NPs were examined by FT-IR, XRD, EDX and TEM. The optimized conditions were determined for the immobilization step. The thermal, pH and storage stability of immobilized PPL were measured and compared with the free PPL. The results represented the substantial enhancement of these stabilities due to immobilization. The measurement of Michaelis-Menten parameters (K m and V max) also revealed the considerable improvement of immobilized PPL. © 2011 Elsevier B.V.
Electrochimica Acta (00134686) (11)
A silica gel-modified carbon paste electrode (Si-CPE) was fabricated and used for selective and sensitive determination of insulin. The experimental results suggested that insulin effectively accumulated on surface of the modified electrode resulting in a marked enhancement of its oxidation current response. Therefore, the modified electrode was used as an electrochemical sensor for the differential pulse adsorptive stripping voltammetric and hydrodynamic amperometric determination of insulin. The influence of various experimental parameters on the voltammetric response of insulin was investigated. Using hydrodynamic amperometry, under optimum conditions, calibration plot for insulin was linear in the range of 90-1400 pM. The sensitivity and detection limit of the proposed amperometric method were found to be 107.3 pA/pM (1511.3 pA/pM cm2) and 36 pM, respectively. The electrode has the remarkable advantages of simple preparation using inexpensive material, high reproducibility, good chemical and mechanical stabilities, and easy surface renewal owing to bulk modification. The high selectivity of the modified electrode towards oxidation of insulin in the presence of sulfur containing amino acids including cystine, cysteine, and glutathione is a key advantage of the proposed electrode. © 2010 Elsevier Ltd.
Electrochimica Acta (00134686) (24)
In this paper a modification strategy for functionalization of glassy carbon electrode (GCE) with Nile blue (NB) is described. In this strategy the GC electrode was functionalized with 4-nitrophenyl (NP) group by electrochemical reduction of 4-nitrobenzenediazonium salt in nonaqueous media. Then the nitro group was reduced electrochemically to amine functionality. Next modification step was dialdehyde derivatization, in which glutaraldehyde (Glu) was attached to the electrode surface through Schiff base reaction with surface amine groups. The modification was completed by attachment of NB via Schiff base formation between the NB and immobilized Glu. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to trace the reactions in each step. The chemically modified electrode exhibited good electrocatalytic activity for both reduction and oxidation of H2O2. A significant decrease in over voltage for the reduction of hydrogen peroxide, as well as a drastic increase in the peak currents were observed in comparison with the bare GC electrode. These characteristics together with long-term stability, low detection limit, and high sensitivity of the modified electrode are highly promising for amperometric determination of hydrogen peroxide. © 2010 Elsevier Ltd. All rights Reserved.
AIP Conference Proceedings (15517616)
In this report magnetite was synthesized by a coprecipitation method, then coated with a layer of silica. Another layer of mesoporous silica was added by a sol-gel method, then 5-amino-1,3,4-thiadiazole-thiol (ATT) was immobilized onto the synthesized nanoparticles with a simple procedure. This was followed by a series of characterizations, including transmission electron microscopy (TEM), FT-IR spectrum, elemental analysis and XRD. Heavy metal uptake of the modified nanoparticles was examined by atomic absorption spectroscopy. For further investigation we chose Cu2+ as the preferred heavy metal to evaluate the amount of adsorption, as well as the kinetics and mechanism of adsorption. Finally, the capacity of our nanoparticles for the heavy metal removal from blood was shown. We found that the kinetic rate of Cu2+ adsorption was 0.05 g/mg/min, and the best binding model was the Freundlich isotherm. © 2010 American Institute of Physics.
Electrochimica Acta (00134686) (28)
Amorphous silica gel modified carbon paste electrode (CPE) offers substantial improvements in voltammetric sensitivity and selectivity towards determination of dopamine (DA). Cyclic voltammetry of Fe(CN)63-/4- as a negatively charged probe revealed that the surface of the silica gel modified carbon paste electrode had a high density of negative charge at pH 8.0. Therefore, the modified electrode adsorbed DA (pKa = 8.9) and enhanced its voltammetric response while repulsed ascorbic acid (AA) (pKa = 4.2) and uric acid (UA) (pKa = 5.4) and inhibited their interfering effects. The influence of various experimental parameters including percent of silica gel in the CPE, pH of solution, and accumulation time and potentials, on the voltammetric response of DA was investigated. At the optimum conditions, the analytical curve was linear for dopamine concentrations from 2.0 × 10-7 to 1.0 × 10-6 mol L-1 and 2.0 × 10-6 to 1.5 × 10-4 mol L-1 with a detection limit (3σ) of 4.8 × 10-8 mol L-1. The prepared electrode was used for determination of DA spiked into DA injection and human serum samples, and very good recovery results were obtained over a wide concentration range of DA. © 2009 Elsevier Ltd. All rights reserved.
Electrochimica Acta (00134686) 54(12)pp. 3495-3500
[PFeW11O39]4- (PFeW11) supported on the surface of 3-aminopropyl(triethoxy)silane modified silica gel was synthesized and used as a bulk modifier to fabricate a renewable three-dimensional chemically modified electrode. The electrochemical behavior of the modified electrode was investigated. Cyclic voltammetry studies showed that the PFeW11 on the electrode surface sustained the same electrochemical properties as that of the PFeW11 in solution. The preparation of chemically modified electrode is simple and quiet reproducible using inexpensive material. The modified electrode had high electrocatalytic activity toward H2O2 reduction and it was successfully applied as an electrochemical detector to monitor H2O2 in flow injection analysis (FIA). The electrocatalytic peak current was found to be linear with the H2O2 concentration in the range 10-200 μmol L-1 with a correlation coefficient of 0.998 and a detection limit (3σ) of 7.4 μmol L-1 H2O2. The electrode has the remarkable advantage of surface renewal owing to bulk modification, as well as simple preparation, good mechanical and chemical stability and reproducibility. © 2009 Elsevier Ltd. All rights reserved.
Bioelectrochemistry (15675394) (2)
Zirconium phosphated amorphous silica gel (devoted briefly as Si-ZrPH) modified carbon paste electrode (CPE) was used for detection of dopamine (DA) in the presence of ascorbic acid (AA) and uric acid (UA). Cyclic voltammetry demonstrated improved reversibility of the DA on the modified electrode. Cyclic voltammetry of Fe(CN)63-/4- as a negatively charged probe revealed that the surface of the Si-ZrPH modified CPE surface had a high density of negative charge. As a result, the modified carbon paste electrode could inhibit the voltammetric response of AA and UA while the redox reaction of dopamine was promoted. Based on this, a selective method has been developed to detect DA in the presence of 2500 and 1000 time higher concentration of AA and UA, respectively. The effect of various experimental parameters on the voltammetric response of dopamine was investigated. Under the chosen conditions, the differential pulse voltammetry peak current was found to be linear with DA concentration in the ranges of 0.04 to 50 μM and 50 to 400 μM. The detection limit of the proposed method in the presence of 100 μM of AA and 40 μM of UA was found to be 0.02 μM for DA determination. Satisfying results are achieved when detecting the DA in injection and human serum samples. © 2009 Elsevier B.V. All rights reserved.
Applied Catalysis A: General (0926860X) (1-2)
The catalytic activity of a hybrid compound, nickel(salen)-POM (1), consisting of nickel(salen) [salen = N,N′-bis(salicylidene)ethylenediamine] complex covalently linked to a lacunary Keggin-type polyoxometalate, K8[SiW11O39] (POM), was studied in the epoxidation of various olefins in acetonitrile, using hydrogen peroxide as an oxygen source. This is the first time that nickel(salen)-POM has been used as a catalyst for the liquid phase epoxidation of olefins. The complex (1) can catalyze epoxidation of various olefins including non-activated terminal olefins. The effect of reaction parameters such as temperature, solvent and oxidant on the epoxidation of styrene were investigated. In comparison with the corresponding Ni(salen), the higher yields obtained in the epoxidation of olefins catalyzed by nickel(salen)-POM. © 2007.
Talanta (00399140) 74(4)pp. 909-914
α-PW12O40 3- (PW12) supported on the surface of silica gel derivatized by 3-aminopropyl(triethoxy)silane (devoted briefly as SiNH3PW12) was synthesized and used as bulk modifier to fabricate a renewable three-dimensional chemically modified electrode. The electrochemical behavior of the modified electrode was characterized by cyclic voltammetry. There is an ionic bonding character between PW12 and the surface amino groups of modified silica, which greatly improves the stability of SiNH3PW12-modified carbon paste electrode due to insolubility of silica gel in water. The SiNH3PW12 bulk-modified carbon paste electrode not only maintains the electrochemical activity of PW12, but also exhibits remarkable advantages of renewability, as well as simple preparation and inexpensive material. The modified electrode offers an excellent and stable electrocatalytic response for the reduction of IO3 - and hydrogen peroxide. The SiNH3PW12-CPE is successfully applied as an electrochemical detector to monitor IO3 - in flow injection analysis (FIA). The catalytic peak current was found to be linear with the IO3 - concentration in the range 5 × 10-6 to 1 × 10-3 mol L-1. The detection limit of the proposed method was found to be 3.1 × 10-6 mol L-1 for IO3 - determination. © 2007 Elsevier B.V. All rights reserved.
Ultrasonics Sonochemistry (13504177) (4)
Vanadium polyoxometalate (PVMo) supported on mesoporous MCM-41, MCM-41-NH2, as efficient and heterogeneous catalysts, with large surface area, for hydrocarbon oxidation with hydrogen peroxide is reported. Oxidation of the alkenes and alkanes gave product selectivities, which are similar to those observed for corresponding homogeneous catalyst. PVMo-MCM was prepared by introduction of PVMo into the mesoporous molecule sieves of MCM-41 by impregnation and adsorption techniques. The samples were characterized by X-raydiffraction (XRD), thermal gravimetric-differential thermal analysis (TG-DTA), FT-IR, scanning electron microscopy (SEM), UV-Vis and cyclic voltametry (CV). Ultrasonic irradiation has a particular effect on MCM-41 structural uniformity and reduced the reaction times and improved the product yields. In addition, the solid catalysts could be recovered and reused several times without loss of its activity. © 2007 Elsevier B.V. All rights reserved.
Catalysis Communications (15667367) (6)
In the present work, efficient epoxidation of olefins with hydrogen peroxide catalyzed by Na5[PV2Mo10O40] supported on TiO2 nanoparticles, PVMo-TiO2, in acetonitrile is reported. The PVMo-TiO2 catalyst was characterized by elemental analysis, FT-IR, UV-Vis, XRD, CV and SEM techniques. Ultrasonic irradiation increased the catalytic activity of the catalyst, reduced the reaction times and increased the products yields. The catalyst was reused several times without significant loss of its catalytic activity. © 2007 Elsevier B.V. All rights reserved.
Analytica Chimica Acta (00032670) (1)
Titanium phosphate grafted on the surface of silica gel (devoted briefly as Si-TiPH) was synthesized and used as bulk modifier to fabricate a renewable three-dimensional chemically modified electrode. The Si-TiPH bulk modified carbon paste electrode was used for the selective determination of dopamine (DA) in the presence of ascorbic acid (AA). The modified electrode offers an excellent and stable response for the determination of DA in the presence of AA. The differential pulse voltammetry peak current was found to be linear with the DA concentration in the range 2 × 10-7 to 1 × 10-6 and 2 × 10-6 to 6 × 10-5 mol L-1. The detection limit of the proposed method in the presence of 2.0 × 10-5 M of AA was found to be 4.3 × 10-8 mol L-1 for DA determination. The proposed method was successfully applied for the determination of DA in injections. © 2007 Elsevier B.V. All rights reserved.
Electroanalysis (10400397) (9)
A novel, sensitive and selective adsorptive stripping procedure for simultaneous determination of iron, copper and cadmium is presented. The method is based on the adsorptive accumulation of thymolphthalexone (TPN) complexes of these elements onto a hanging mercury drop electrode, followed by reduction of adsorbed species by voltammetric scan using differential pulse modulation. The influences of control variables on the sensitivity of the proposed method for the simultaneous determination of iron, copper and cadmium were studied using the Derringer desirability function. The optimum analytical conditions were found to be TPN concentration of 2.0 μM, pH of 9.5, and accumulation potential at -0.4 V vs. Ag/AgCl with an accumulation time of 60 s. The peak currents are proportional to the concentration of iron, copper and cadmium over the 1-80, 0.5-100 and 1-100 ng mL-1 ranges with detection limits of 0.5, 0.4 and 0.9 ng mL-1, respectively. The R.S.D. at a concentration level of 20 ng mL-1 of iron, copper and cadmium were 2.5%, 0.9% and 1.5% (n = 6), respectively. The procedure was applied to the simultaneous determination of iron, copper and cadmium in the tap water and some synthetic samples with satisfactory results. © 2007 Wiley-VCH Verlag GmbH & Co. KGaA.
Analytical Letters (1532236X) (14)
A carbon paste electrode modified with organically functionalized silica was used for the determination of lead. The measurements were carried out in three steps including an open circuit accumulation followed by electrolysis of accumulated lead at the carbon paste electrode and differential pulse voltammetric determination. The effects of several experimental variables such as carbon paste composition, pH and concentration of supporting electrolyte, electrolysis potential, and electrolysis time were studied. The resulting electrode demonstrates linear response over a wide range of Pb(II) concentration (5-1000 ng mL-1) with an accumulation time of 60 sec. The effects of potential interfering ions were studied, and it was found that the proposed procedure is free from most interferences. Long lifetime and rapid and convenient renewal of electrode surface allows the use of a single modified electrode surface in multiple analytical determinations over at least 4 months. The prepared electrode was used for determination of lead spiked in a hair sample, and very good recovery results were obtained over a wide concentration range of lead. Copyright © Taylor & Francis Group, LLC.
Sensors and Actuators, B: Chemical (09254005) (1)
A carbon paste electrode modified with zirconium phosphated-silica was used for the determination of cadmium. The measurements were carried out in three steps including an open circuit accumulation, subsequent electrolysis of accumulated cadmium at the carbon paste electrode, and differential pulse voltammetric determination. The effects of several experimental variables such as carbon paste composition, pH of solution at the accumulation step, pH and concentration of supporting electrolyte, electrolysis potential, accumulation time and electrolysis time were studied. The resulting electrode demonstrated linear response over a wide range of Cd(II) concentration (3-1400 ng mL-1) with an accumulation time of 120 s. The effects of potential interfering ions were studied, and it was found that the proposed procedure was free from most interferences. The prepared electrode was used for determination of cadmium in some artificial synthetic samples, and very good recovery results were obtained over a wide concentration range of cadmium. © 2005 Elsevier B.V. All rights reserved.
Analytical Sciences (09106340) (7)
A novel, sensitive and selective adsorptive stripping procedure for simultaneous determination of copper, bismuth and lead is presented. The method is based on the adsorptive accumulation of thymolphthalexone (TPN) complexes of these elements onto a hanging mercury drop electrode, followed by reduction of adsorbed species by voltammetric scan using differential pulse modulation. The influences of control variables on the sensitivity of the proposed method for the simultaneous determination of copper, lead and bismuth were studied using the Derringer desirability function. The optimum analytical conditions were found to be TPN concentration of 4.0 μM, pH of 9.0, and accumulation potential at -800 mV vs. Ag/AgCl with an accumulation time of 80 s. The peak currents are proportional to the concentration of copper, bismuth and lead over the 0.4 - 300, 1 - 200 and 1 - 100 ng mL-1 ranges with detection limits of 0.4, 0.8 and 0.7 ng mL-1, respectively. The procedure was applied to the simultaneous determination of copper, bismuth and lead in the tap water and some synthetic samples with satisfactory results. 2006 © The Japan Society for Analytical Chemistry.
Journal of the Iranian Chemical Society (1735207X) (1)
Molybdenum is determined by adsorptive cathodic stripping voltammetry in 0.15 M nitric acid solution containing 15 μM 2',3,4',5,7-pentahydroxyflavone (morin) as a ligand. In this medium, molybdenum is preconcentrated on a hanging mercury drop electrode and stripped cathodically in square-wave voltammetry mode, with a peak potential of -350 mV vs. Ag/AgCl (saturated KCl). The effect of various parameters (ligand concentration, supporting electrolyte composition, accumulation potential and collection time) on the sensitivity and linear range of the calibration curve are discussed. With controlled accumulation for 1 min, the detection limit (3c) was 0.45 ng ml-1 molybdenum and the calibration curve is linear up to 70 ng ml-1 The procedure is applied to the determination of molybdenum in real samples with satisfactory results.
Separation and Purification Technology (13835866) (2)
Solvent extraction of cadmium from aqueous hydrochloric acid media (1-11 mol dm-3) into dichloromethane solution of 18-crown-6, dibenzo-18-crown-6 and dicyclohexyl-18-crown-6 (DC18C6) has been studied at 25 °C. The highest extraction abilities have been found by DC18C6 in the range of 6-7 mol dm-3 hydrochloric acid. The conventional log-log plot analysis of the extraction equilibrium data at 3 and 8 mol dm-3 of the acid revealed that the cadmium ions were extracted as ion-pairs [HL+][CdCl3-] and [HL+]2[CdCl42-] (L = DC18C6), respectively. The effect of diluent has been investigated using chloroform, dichloromethane, 1,2-dichloroethane, carbon tetrachloride and toluene. The extraction of the cadmium increased with diluent polarity. The ability of DC18C6 to separate cadmium from binary mixtures of Cd and M (M = Ni, Mn, Co, Zn, Pb and Fe) has been evaluated. The efficiency and selectivity of the method allow to propose it for the recovery of cadmium from consumed Ni-Cd rechargeable batteries. © 2004 Elsevier B.V. All rights reserved.
Electroanalysis (10400397) (17)
Simultaneous determination of bismuth and copper by anodic stripping voltammetry using H-point standard addition method (HPSAM) with simultaneous addition of analytes is described. The effect of various parameters including acid concentration, accumulation time, accumulation potential and concentration ratio of analytes in the standard solution on the sensitivity and accuracy of method were investigated. The results of applying the H-point standard addition method showed that Cu2+ and Bi3+ could be determined simultaneously with the concentration ratios of Cu2+ to Bi 3+ varying from 1:15 to 16:1 in the mixed sample. The method was successfully applied to the simultaneous determination of copper and bismuth in some synthetic mixtures. © 2005 Wiley-VCH Verlag GmbH & Co. KGaA.
The applicability of H-point standard addition method (HPSAM) to the resolving of overlapping differential pulse anodic stripping voltammetric peaks corresponding to the oxidation of lead and tin is verified. The results show that the H-point standard addition method is suitable for the simultaneous determination of lead and tin in aqueous media. The results of applying the H-point standard addition method showed that Sn2+ and Pb2+ could be determined simultaneously with the concentration ratios of Sn 2+ to Pb2+ varying from 1:5 to 10:1 in the mixed sample. The proposed method has been successfully applied to the simultaneous determination of lead in the presence of tin in some synthetic samples. Moreover, the applicability of the method was demonstrated by the recovery of lead in a canned soft drink sample. © 2003 Elsevier B.V. All rights reserved.
Analytica Chimica Acta (00032670) (1)
A sensitive and selective method for the simultaneous determination of copper, zinc and lead is presented. The method is based on the adsorptive accumulation of 2′,3,4′,5,7-pentahydroxyflavone (Morin) complexes of these elements onto a hanging mercury drop electrode, followed by reduction of adsorbed species by voltammetric scan using differential pulse modulation. Optimal analytical conditions were found to be Morin concentration of 2.0μM, pH of 4.0, and an adsorption potential at -500mV versus Ag/AgCl. With an accumulation time of 60s, the peak currents are proportional to the concentration of copper, lead and zinc over the 1 to 60, 0.3-80 and 1-70ngml-1 range with detection limits of 0.06, 0.08 and 0.06ngml-1, respectively. The procedure was applied to the simultaneous determination of copper, lead and zinc in some real and synthetic artificial real samples with satisfactory results. © 2003 Elsevier B.V. All rights reserved.
Analytica Chimica Acta (00032670) (1)
A new method is presented for the determination of bismuth and copper based on cathodic adsorptive stripping of complexes of Cu(II) and Bi(III) with 2′,3,4′,5,7-pentahydroxyflavone (morin) at a hanging mercury drop electrode (HMDE). The effect of various parameters such as pH, concentration of morin, accumulation potential and accumulation time on the selectivity and sensitivity were studied. The optimum conditions for determination of copper include nitric acid concentration 0.1M, morin concentration 0.6μM and accumulation potential of -300mV. Those conditions for the determination of bismuth include 0.15M acid concentration, 0.6μM morin and accumulation potential of -300mV. Under these optimum conditions and for an accumulation time of 60s, the measured peak current at -20 to 25mV is proportional to the concentration of copper and bismuth over the range of 0.2-130 and 5-50ngml -1, respectively. At high concentration of morin (35μM morin) and accumulation potential of -300mV (versus Ag/AgCl reference electrode) the peak current is proportional only to the concentration of copper and bismuth has no contribution to the current. At low concentration of morin (0.5μM morin) and accumulation potential of 100mV (versus Ag/AgCl reference electrode) the peak current is proportional only to the concentration of bismuth. The method was applied to the determination of copper and bismuth in some real and synthetic samples with satisfactory results. © 2003 Elsevier B.V. All rights reserved.
Electroanalysis (10400397) (13)
An electrochemical adsorptive stripping approach is presented for the trace measurement of copper. The method is based on the reduction of Cu(II) at pH 4.3 adenine (Ade) containing solution at - 90 mV (vs. SCE), adsorption of Cu-Ade complex on hanging mercury drop electrode (HMDE) and the voltammetric determination by further reduction to Cu(0) at HMDE. Experimental optimum conditions were determined in the fundamental studies. The results show that the best base solution consists of 0.05 mol L-1 acetate buffer solution (pH 4.3) and 8 × 10-6 mol L-1 adenine. For an accumulation period of 120 s, the linear range and the detection limit were found as 1.5 × 10-9 -4.5 × 10-8 mol L-1 and 5 × 10-10 mol L-1, respectively. The relative standard deviation (RSD) for determination of 1 × 10-8 mol L-1 was 5% (n = 5). The method has been applied to the analysis of copper in analytical reagent grade salts and also in cow's liver tissue with satisfactory results.
Analytical Sciences (09106340) (9)
Trace amounts of thallium(I) can be determined using adsorptive cathodic stripping voltammetry in the presence of Xylenol Orange (XO). The reduction current of the thallium(I)-XO complex ion was measured by square-wave cathodic stripping voltammetry. The peak potential was at -0.44 V vs. Ag/AgCl. The effect of various parameters (pH, ligand concentration, accumulation potential and collection time) on the response are discussed. The response was linearly related to the thallium concentration in the range 0.5 - 110 ng ml-1 and 110 - 2000 ng ml-1. The limit of detection was 0.2 ng ml-1. The relative standard deviation for the determination of 80 ng ml-1 thallium was 2.8%. Many common anions and cations did not interfere with the determination of thallium. The interference of lead was reduced by the addition of 0.003 M sodium carbonate. The voltammetric procedure was then successfully applied to the determination of thallium in various complex samples.
Electroanalysis (10400397) (10)
The electrochemical properties of glutathione (GSH) monolayer on the surface of a hanging mercury drop electrode were studied. It was found that the GSH monolayer could not block out the electron transfer completely so that a multilayer built up on the electrode surface. The GSH molecules had the expansion-contraction response depending on pH value.
Electroanalysis (10400397) (13)
Controlled adsorptive accumulation of bismuth (III) complexed with alizarine red S (ARS) on a hanging mercury drop electrode provides the basis for the direct stripping measurement of this element in the nanomolar concentration level. The reduction current of adsorbed complex ions of bismuth is measured by differential pulse cathodic stripping voltammetry, preceded by an accumulation period of one minute. The peak potential is at 0.05 V (vs. Ag/AgCl). Optimal experimental parameters were found to be an ARS concentration of 15 μM, an accumulation potential of -0.2 V, and an acid concentration of 0.10 M (nitric acid). The limit of detection (3σ) is 0.5 nM, and the response is linear up to 150 nM. Many common anions and cations do not interfere in the determination of bismuth. An intercomparison of bismuth determinations performed by the proposed method and previously electroanalytical methods demonstrates higher selectivity, and shorter analysis time of this method. The voltammetric procedure was then applied successfully to the determination of bismuth in various complex samples.
Iranian Journal Of Chemistry And Chemical Engineering (10219986) (2)
The reduction mechanism of molybdenum-methyl thymol blue (MTB)-chlorate system has been investigated in water on a mercury electrode. As this system is very sensitive for ultra-trace determination of molybdenum, the actual mechanism involved was studied. Electrochemical techniques, including dc fast polarography and cyclic voltammetry were employed. It is shown that, the cathodic wave of molybdenum in the presence of methyl thymol blue and chlorate has an adsorptive catalytic character.
Analytical Letters (00032719) (3)
A technique is presented for the determination of trace amounts of copper(II) by adsorptive cathodic stripping voltammetry. The procedure is based on adsorptive accumulation of copper(II)-Alizarin Red S (ARS) complex on a hanging mercury drop electrode, followed by a stripping voltammetric measurement of the reduction current of the adsorbed complex at -0.16 V (vs. Ag/AgCl). The height of the copper -ARS reduction peak is linearly dependent upon the copper(II) concentration between 0.2-15 and 15-500 ng.ml-1. The detection limit of the technique is 0.05 ng.ml-1 copper(II) for a collection time of 1 minute. The method is free from most interferences. The procedure has been successfully applied to the determination of trace mounts of copper(II) in some analytical grade salts.
Analytica Chimica Acta (00032670) (1-2)
A highly selective and sensitive method is presented for the determination of V(IV), based on its catalytic effect on the oxidation reaction of aniline blue by bromate. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of aniline blue at 591nm, between 0.5 to 5min (the fixed time method). The effect of various parameters such as pH, concentrations of bromate and aniline blue, temperature and ionic strength on the rate of reaction were studied. The method is free from most interferences, especially from large amounts of V(V). The decrease of absorbance is proportional to the concentration of V(IV) over the entire concentration range tested (5-1200ngml-1) with a 3σ detection limit of 2.0ngml-1 and a relative standard deviation at 60-200ngml-1 V(IV) of ca. 3% (n=3).The method was applied to the determination of V(IV) in river water and some synthetic samples with satisfactory results. Copyright (C) 2000 Elsevier Science B.V.
A very sensitive and selective catalytic adsorptive cathodic stripping procedure for trace measurements of cobalt is presented. The method is based on adsorptive accumulation of the cobalt-MTB (methyl thymol blue) complex onto a hanging mercury drop electrode, followed by reduction of the adsorbed species by voltammetric scan using differential pulse modulation. The reduction current is enhanced catalytically by nitrite. The optimum conditions for the analysis of cobalt include pH 9.0 (ammonia buffer), 2.0 μM methyl thymol blue, 0.8 M sodium nitrite and an accumulation potential of -0.5 V (versus Ag/AgCl). The peak current is proportional to the concentration of cobalt over the entire concentration range tested (0.02-500 ng ml-1) with a detection limit of 0.005 ng ml-1 for an accumulation time of 60 s. The method was applied to determination of cobalt in a mineral water sample and some analytical grade salts with satisfactory results. (C) 2000 Elsevier Science B.V.
Analytica Chimica Acta (00032670) (1-3)
A sensitive and selective procedure is presented for the voltammetric determination of copper. The procedure involves an adsorptive accumulation of copper pyrogallol red on a hanging mercury drop electrode, followed by a stripping voltammetric measurement of reduction current of adsorbed complex at -0.2V (vs. Ag/AgCl). The optimum conditions for the analysis of copper include pH (3.0-4.5), 20μM pyrogallol red and an accumulation potential of -0.1V (vs. Ag/AgCl). The peak current is proportional to the concentration of copper over the range 0.4-60ngml-1 with a detection limit of 0.07ngml-1 with an accumulation time of 60s. The method was applied to the determination of copper in some analytical grade salts and also in cow's liver tissue. Copyright (C) 1999 Elsevier Science B.V.
Fresenius' Journal of Analytical Chemistry (09370633) (6)
A sensitive kinetic spectrophotometric method has been developed for the determination of Se(IV) over the range of 45 to 4000 ng in 10 mL of solution. The method is based on the catalytic effect of Se(IV) on the reduction reaction of bromate by hydrazinium dichloride, with subsequent reaction of Ponceau S with products of the above reaction (chlorine and bromine), causing color changing of Ponceau S. Method development includes optimization of time interval for measurement of slope, pH, reagents concentration, and temperature. The optimized conditions yielded a theoretical detection limit of 33 ng/ 10 mL of solution of Se(IV). The interfering effects were studied and removed. The method was applied to the determination of selenium in spiked water, Kjeldahl tablet, selenium tablet, and shampoo. Vanadium(V) has an inhibition effect on the catalyzed reaction of bromate and hydrazine by selenium. Using this effect, V(V) can be determined in the range of 70 to 2500 ng in 10 mL of solution. The optimization procedure includes pH and selenium concentration. An extraction method was used for interference removal. The method was applied to the determination of vanadium in petroleum. © Springer-Verlag 1999.
Journal of Membrane Science (03767388) (2)
The facilitated transport of Au(III) from cyanide solutions through a bulk liquid membrane is reported. The organic phase consisted of a chloroform solution containing Victoria blue dye as the Au(CN)-4 carrier. The effects of pH of source phase, potassium cyanide concentration in source phase, Victoria blue concentration in the organic phase and sodium hydroxide in the receiving phase on the efficiency of transport process were examined. Under optimum conditions the extent of Au(CN)-4 transport across the liquid membrane was about 97% after 180min. The carrier can selectively and efficiently transport Au(CN)-4 ion from the aqueous solutions containing other cations such as alkali and alkaline earth, Zn2+, Pb2+, Cu2+, Cd2+, Hg2+, Ag+, Co2+, Fe2+, Pt2+, Pd2+ and Ni2+. Copyright (C) 1999 Elsevier Science B.V.
Analytica Chimica Acta (00032670) (2-3)
A highly selective and sensitive procedure is presented for the determination of ultra-trace concentrations of molybdenum by catalytic adsorptive stripping voltammetry. The method is based on adsorptive accumulation of the molybdenum (Mo)-methyl thymol blue (MTB) complex onto a hanging mercury drop electrode, followed by reduction of the adsorbed species by voltammetric scan using differential pulse modulation. The reduction current is enhanced catalytically by chlorate. Optimal analytical conditions were found to be a MTB concentration of 0.8μM, pH 2.5, a chlorate concentration of 0.5M, and an adsorption potential at 100mV versus Ag/AgCl. The peak current is proportional to the concentration of molybdenum over the range 0.01-150ngml-1 with a 3σ detection limit of 2pgml-1 with an accumulation time of 60s. The effects of possible interfering ions were studied, and it was found that the proposed procedure is free from interferences of common interfering elements such as tungsten, and iron. The procedure is applied to the determination of molybdenum in a mineral water sample and some analytical grade salts with satisfactory results. Copyright (C) 1999 Elsevier Science B.V.
Transport of Ag+ as Ag(CN)2 - ions through a bulk liquid membrane is reported. The bulk liquid membrane used is a solution of Victoria blue (VB) in chloroform. The effects of pH of the source phase, cyanide concentration in the source phase, sodium hydroxide in the receiving phase, and VB concentration in the organic phase on the efficiency of the transport system were studied. The above system has a high selectivity for Ag+ and can selectively and efficiently transport Ag(CN)2 - ion from aqueous solutions containing other cations such as alkali and alkaline earths, Zn2+, Pd2+, Cu2+, Cd2+, Hg2+, Co2+, Fe2+, Pb2+, Ni2+, and Al3+.
Journal of Membrane Science (03767388) (1-2)
Methyl red was used as an excellent carrier for the uphill transport of Hg(II) through bulk liquid membrane. By using iodide as a metal acceptor and in the presence of sulfuric acid in receiving phase the amount of mercury transport across the bulk liquid membrane was about 90% after 180 min. By replacement of the above receiving phase with 0.45 M HCl, a simpler and more reproducible system was obtained. Oleic acid was used to overcome a minor leaching of the carrier into the aqueous phase at high acid concentration. This system was optimized with a simplex optimization program. Under optimum conditions, the amount of Hg(II) transport across the liquid membrane is about 80% after 150 min. The carrier can selectively and efficiently transport Hg2+ ion from aqueous solution containing other cations such as Cd2+, Zn2+, Cu2+, Mg2+, Ca2+, Ag+, Ni2+, Al3+, Na+, Pb2+, Fe3+ and Pd2+.
