Coated,Wire-Based,New Schiff Base Potentiometric Sensor for Lead(II) Ion

An ion-selective electrode for lead(II) based on a dispersion of N,N"-bis(3-methyl salicylidine)-p-phenyl methane diamine particles into a polymeric membrane using coated-wire configuration is described. Membranes based on polyvinyl chloride containing different amounts of plasticizer and ionophore are studied. The best performance in terms of slope (30.3 ± 0.6 mV per decade) and response time (<15 s) is displayed. The sensor shows a Nernstian response for Pb(II) ions over a wide concentration range of 2.0 × 10^–5 to 0.10 M. The sensors can be used for more than three months without any considerable divergence in potentials. The selectivity is also good towards the most common univalent and divalent cations and the signal is constant in the pH range 1.6–6.0. An application to lead determination in mineral rocks and wastewater proved to be a success, and it was employed as an indicator electrode in potentiometric titration of CrO^2– ₄ with lead ions.     

Convenient Synthesis of 14‐Aryl‐14‐H‐dibenzo[a,j]xanthenes Catalyzed by Acyclic Brønsted Acidic Ionic Liquid [H—NMP]+[HSO4]− under Microwave Irradiation

Efficient method for direct preparation of 14‐aryl‐14‐H‐dibenzo[a,j]xanthenes through condensation of β‐naphthol with various aromatic aldehydes in the presence of the catalytic amount of [H—NMP]⁺[HSO₄]^? under microwave irradiation was described. This method has the advantages such as; very easy reaction workup, absolute separation of catalyst from the reaction mixture and smooth recyclability of catalyst. In this reaction 14‐aryl‐14‐H‐dibenzo[a,j]xanthenes were obtained as desired products in excellent yields and short reaction times via green and one‐pot procedure.     

Electrochemical determination of captopril in the presence of acetaminophen,tryptophan, folic acid,and l-cysteine at the surface of modified carbon nanotube paste electrode

Ionics - A novel carbon paste electrode (CPE) modified with 2,2′-[1,7–heptanediylbis(nitrilomethylidene)]-bis(4-hydroxyphenol) (DHB) and carbon nanotubes (CNTs) was prepared. At first,...     

Montmorillonite as a Heterogeneous Catalyst in the Efficient,Mild and One Pot Synthesis of Schiff Bases under Solvent‐Free Conditions

A mild and efficient method has been reported for preparation of Schiff base ligands through condensation reaction of various aromatic aldehydes and ketones with different aromatic amines in the presence of montmorillonite as a heterogeneous catalyst under solvent free conditions. The advantages of this friendly, economically, environmentally and mild method are such as; simplicity of the reaction procedure, reusability of catalyst, simple work‐up, high product yields and very short reaction times.     

Determination of nickel in natural waters by FAAS after sorption on octadecyl silica membrane disks modified with a recently synthesized Schiff's base

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.     

A study of the electrochemical behavior of an oxadiazole derivative electrodeposited on multi-wall carbon nanotube-modified electrode and its application as a hydrazine sensor

In this study, an oxadiazole multi-wall carbon nanotube-modified glassy carbon electrode (OMWCNT−GCE) was used as a highly sensitive electrochemical sensor for hydrazine determination. The surface charge transfer rate constant, k _s, and the charge transfer coefficient, α, for electron transfer between GCE and electrodeposited oxadiazole were calculated as 19.4 ± 0.5 s⁻¹ and 0.51, respectively at pH = 7.0. The obtained results indicate that hydrazine peak potential at OMWCNT−GCE shifted for 14, 109, and 136 mV to negative values as compared with oxadiazole-modified GCE, MWCNT−GCE, and activated GCE surface, respectively. The electron transfer coefficient, α, and the heterogeneous rate constant, k′, for the oxidation of hydrazine at OMWCNT−GCE were also determined by cyclic voltammetry measurements. Two linear dynamic ranges of 0.6 to 10.0 μM and 10.0 to 400.0 μM and detection limit of 0.17 μM for hydrazine determination were evaluated using differential pulse voltammetry. In addition, OMWCNT−GCE was shown to be successfully applied to determine hydrazine in various water samples.

     

Facile and Mild Synthesis and Characterization of Some New Diazo Dyes on the Basis of Schiff Bases in the Presence of Nanocrystalline Magnesium Oxide as a Base Catalyst under Solvent‐free Conditions

In this research, some new diazo dyes including Schiff base have been synthesized by the condensation reaction between ethylenediamine and derivatives of salicylaldehyde containing diazo functional groups in the presence of nanocrystalline magnesium oxide as a solid base catalyst under solvent‐free conditions. Nanocrystalline magnesium oxide has been characterized by XRD, BJH and TEM techniques. The corresponding products have been obtained in excellent yields and high purity. All of the obtained diazo‐Schiff bases are highly colored and can be applicable as useful diazo dyes and characterized by spectroscopy data.     

A study of the electrochemical behavior of an oxadiazole derivative electrodeposited on multi-wall carbon nanotube-modified electrode and its application as a hydrazine sensor

In this study, an oxadiazole multi-wall carbon nanotube-modified glassy carbon electrode (OMWCNT?GCE) was used as a highly sensitive electrochemical sensor for hydrazine determination. The surface charge transfer rate constant, k _s, and the charge transfer coefficient, ??, for electron transfer between GCE and electrodeposited oxadiazole were calculated as 19.4?±?0.5?s^?1 and 0.51, respectively at pH?=?7.0. The obtained results indicate that hydrazine peak potential at OMWCNT?GCE shifted for 14, 109, and 136?mV to negative values as compared with oxadiazole-modified GCE, MWCNT?GCE, and activated GCE surface, respectively. The electron transfer coefficient, ??, and the heterogeneous rate constant, k??, for the oxidation of hydrazine at OMWCNT?GCE were also determined by cyclic voltammetry measurements. Two linear dynamic ranges of 0.6 to 10.0???M and 10.0 to 400.0???M and detection limit of 0.17???M for hydrazine determination were evaluated using differential pulse voltammetry. In addition, OMWCNT?GCE was shown to be successfully applied to determine hydrazine in various water samples.