Simple and efficient protocol for the synthesis of benzoxazole,benzoimidazole and benzothiazole heterocycles using Fe(Ⅲ)–Schiff base/SBA-15 as a nanocatalyst

Benzimidazoles, benzoxazoles, and benzothiazoles derivatives were synthesized from condensation of aldehydes and 1,2-phenylenediamine or ortho-aminophenol or ortho-aminothiophenol in the presence of catalytic amount of Fe(Ⅲ)–Schiff base/SBA-15 in water medium. Short reaction times, good to excellent yields, easy availability, reusability, and use of an eco-friendly catalyst are some of the significant attributes of the present method.     

Construction of a new Cu2+ coated wire ion selective electrode based on 2-((2-(2-(2-(2-hydroxy-5-methoxybenzylidene amino)phenyl)disufanyl)phenylimino)methyl)-4-methoxyphenol Schiff base

In this article a new coated platinum Cu²⁺ ion selective electrode based on 2-((2-(2-(2-(2-hydroxy-5-methoxybenzylideneamino)phenyl)disufanyl)phenylimino) methyl)-4-methoxyphenol Schiff base (L₁) as a new ionophore is described. This sensor has a wide linear range of concentration (1.2 × 10⁻⁷-1.0 × 10⁻¹ mol L⁻¹) and a low detection limit of 9.8 × 10⁻⁸ mol L⁻¹of Cu(NO₃)₂. It has a Nernstian response with slope of 29.54 ± 1.62 mV decade⁻¹ and it is applicable in the pH range of 4.0-6.0 without any divergence in potentioal. The coated electrode has a short response time of approximately 9 s and is stable at least for 3.5 months. The electrode shows a good selectivity for Cu²⁺ ion toward a wide variety of metal ions. The proposed sensor was successfully applied for the determination of Cu²⁺ ion in different real and environmental samples and as indicator electrode for potentiometric titration of Cu²⁺ ion with EDTA.     

Bis(2-mercaptobenzoxazolato)mercury(II) and bis(2-pyridinethiolato)mercury(II) complexes as carriers for thiocyanate selective electrodes

Highly selective poly(vinyl chloride) (PVC) membrane electrodes based on bis(2-mercaptobenzoxazolato)mercury(II) [Hg(MBO)₂] and bis(2-pyridinethiolato)mercury(II) [Hg(PT)₂] complexes as new carriers for thiocyanate-selective electrodes are reported. The electrodes were prepared by coating the membrane solution containing PVC, plasticizer, carriers and additives on the surface of graphite electrodes. Influence of the membrane composition, pH and possible interfering anions were investigated on the response properties of the electrodes. Both sensors exhibited Nernstian responses towards thiocyanate over a wide concentration range of 1×10⁻⁶ to 0.1 M, with slopes of 60.6±0.8 and 57.5±1.2 mV per decade of thiocyanate concentration for Hg(MBO)₂ and Hg(PT)₂ carriers, respectively, over a wide pH range of 3-11. The limit of detection for both electrodes was ∼6×10⁻⁷ M. The sensors have response times of ≤5 s and can be used for at least 2 months without any considerable divergence in their potential response. The proposed electrodes show fairly good discrimination of thiocyanate over several inorganic and organic anions. The electrodes were successfully applied to direct determination of thiocyanate in saliva and as indicator electrodes in precipitation titrations.     

Comparison of Activated Carbon,Multiwalled Carbon Nanotubes,and Cadmium Hydroxide Nanowire Loaded on Activated Carbon as Adsorbents for Kinetic and Equilibrium Study of Removal of Safranine O

Activated carbon (AC), multiwalled carbon nanotube (MWCNT), and cadmium hydroxide nanowire loaded on activated carbon (Cd(OH)₂-NW-AC) have been used for the removal of safranine O (SO) from wastewater. The effects of various parameters including pH, temperature, concentration of the dye, amount of adsorbents, and contact time on the SO adsorption efficiency for all adsorbents has been investigated. Graphical correlation of fitting experimental data to various adsorption isotherm models like those of Langmuir, Freundlich, Tempkin, and Dubinin–Radushkevich for all adsorbents have been calculated. It was found that safranine O adsorption on all adsorbents was endothermic and feasible in nature. Fitting the experimental data to different kinetic models suggests that the adsorption process follows pseudo-second-order kinetics with involvement of the particle diffusion mechanism.     

Novel potentiometric sensor for the determination of Cd2+ based on a new nano-composite

A novel ion selective carbon paste electrode for Cd²⁺ ions based on 2,2′-thio-bis[4-methyl(2-amino phenoxy) phenyl ether] (TBMAPPE) as an ionophore was prepared. The carbon paste was made based on a new nano-composite including multi-walled carbon nanotubes (MWCNTs), nanosilica and room-temperature ionic liquid, 1-Butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF₆). The constructed nano-composite electrode showed better sensitivity, selectivity, response time, response stability and lifetime in comparison with typical Cd²⁺ carbon paste sensor for the successful determination of Cd²⁺ ions in water and in waste water samples. The best performance for nano-composite sensor was obtained with an electrode composition of 18% TBMAPPE, 20% BMIM-PF₆, 48% graphite powder, 10% MWCNT and 4% nanosilica. The new electrode exhibited a Nernstian response (29.95?±?0.10?mV?decade^?1) toward Cd²⁺ ions in the range of 3.0?×?10^?8 to 1.0?×?10^?1?mol?L^?1 with a detection limit of 7.5?×?10^?9?mol?L^?1. The potentiometric response of prepared sensor was independent of the pH of test solution in the pH range 3.0 to 5.5. It had a quick response with a response time of about 6?s. The proposed electrode showed fairly good selectivity over some alkali, alkaline earth, transition and heavy metal ions.     

Thiocyanate-selective membrane electrode based on cobalt(III) Schiff base as a charge carrier

A highly selective polyvinylchloride (PVC) membrane electrode based on Schiff base complex i.e. [Cobalt (Salpen) (PBu₃)] ClO4 · H2O (Salpen = bis(salycilaldehyde)propylene diamine) is reported as new carrier for thiocyanate selective electrode by incorporating the membrane ingredients on the surface of graphite electrodes. The proposed electrode possesses a very wide Nernestian linear range to thiocyanate from 1.0 × 10^?6 to 1.0 × 10^?1 M with slope of ?59.05 ± 0.91 mV per decade of thiocyanate concentration, very low detection limit (8.0 × 10^?7 M) and good thiocyanate selectivity over the wide variety of other anions. Fast and stable response, good reproducibility, long-term stability, applicability over a wide pH range (2.8–9.8) are advantages of the reported electrode. The sensor has a response time of <5 s and can be used for at least 14 weeks without any considerable change in respective potential response. The proposed electrode was used for the determination of thiocyanate in saliva, wastewater and human urine with satisfactory results and good agreement with colorimetric as reference method.     

Potentiometric and Spectrophotometric Studies of Copper(II) Complexes of Some Ligands in Aqueous and Nonaqueous Solution

Stoichiometry and equilibrium study of copper‐ligands including mercaptobenzoxazole (MBO), 4‐propyl 2‐thiouracyl (PTU), methyl‐2‐pyridylketone oxime (MPKO), phenyl‐2‐pyridylketone oxime (PPKO), 4,6‐dihydroxy‐2‐mercaptopyrimidine (DHMP), N,N′‐phenylene bis(salicylaldimine) (PBS) and 1,2‐bis(2‐hydroxyphenyl)naphtaldiimine (BHNPDI) were conducted in aqueous and nonaqueous solution by potentiometry and spectrophotometry. Stability constants of the complexes are determined at 25 ± 1 °C and 0.1 or 0.05 M ionic strength in water or acetonitrile solvents. Oximes ligand protonation constants and copper‐ligands complexes' stability and hydrolysis constants were calculated using the BEST program in aqueous solution. The stability constants of copper‐ligands complexes were calculated using the KINFIT program in acetonitrile solution. The results of these two methods are made self‐consistent, then rationalized assuming an equilibrium model including the species, ML, MLH, MLOH and ML₂ (where the charges of the species have been ignored for the sake of simplicity) (L = MBO, PTU, MPKO, PPKO, DHMP, BHNPDI and PBS).     

Adsorptive stripping voltammetric determination of copper(II) ion using phenyl pyridyl ketoneoxime (PPKO)

A sensitive and selective procedure is presented for the voltammetric determination of copper(II) ion. The procedure involves an adsorptive accumulation of Cu2+-PPKO on a hanging mercury drop electrode, followed by a stripping voltammetric measurement of reduction current of adsorbed complex at about -0.30 V (vs. SCE). The optimum conditions for the analysis of copper(II) ion include pH (5.8-7.0), 60 microgM PPKO and an accumulation potential of -0.5 V (vs. SCE). The peak current is proportional to the concentration of copper over the range 0.3-76 ng mL(-1) with a detection limit of 0.01ng mL(-1) with an accumulation time of 60 s. The speciation of different forms of complex between copper(II) ion and PPKO, using the Best (Martell program), followed pH measurement were examined. The method was applied to the determination of copper(II) ion content in real samples successfully.     

Construction of a New Uranyl‐Selective Electrode Based on a New Ionophore: Comparison of the Effect Additive on Electrode Responses

A new plasticized PVC uranyl‐selective electrode based on a bis(2‐hydroxyacetophenone)ethylenediimine (BHAED) carrier by the direct coating of the membrane ingredients on the surface of a graphite disk electrode is reported. The electrode displayed high selectivity for uranyl ion toward a number of inorganic ions. The influence of the membrane compositions and pH, the effect of lipophilic cationic and anionic additives and plasticizer on the response properties of the electrode were investigated. The electrode exhibited a Nernstian slope of + 29.3 ± 1.2 for the uranyl ion concentration in the range of 5.0 × 10^?6 ?0.05 M with detection limits of approx. 2.0 μM. The potentiometric responses of the electrode are independent of pH over the range of 3.0–4.5 with satisfactory reproducibility. The sensor has response times of <5 s and can be used for at least 2 months without considerable divergence in potential.     

Application of novel copper organic material for facile microextraction of sodium valproate from human plasma samples: Experimental design optimization and isotherm study

Well‐designed metal organic materials (MOMs) were synthesized and applied for pre‐concentration and determination of sodium valproate (Na‐VP) from biological samples, bound to the copper complex of 1,4‐phenylenedioxydiacetic acid under mild conditions. The channels of this sorbent provide high efficiency and also selectivity. The MOMs were structurally characterized using Fourier transform infrared and energy‐dispersive X‐ray spectroscopies, scanning electron microscopy and X‐ray diffraction, and they were found to have suitable features for quantification of Na‐VP using HPLC coupled with UV detection at λ = 215 nm. Moreover, the rate of adsorption is improved by ultrasonic power and the experimental data are best fitted according to Freundlich adsorption isotherm. According to the central composite design, the best experimental conditions are 280.0 μl, 3.0 min and 17.0 mg for volume of eluent, sonication time and sorbent mass respectively. Calibration plots show linear responses towards Na‐VP concentrations (0.4–18.0 μg ml^?1), satisfactory limit of detection (0.06 μg ml^?1, S/N = 3) and reasonable enrichment factor (70.58). The coefficient of variation values of both inter‐ and intra‐day analyses were less than 4.0%, indicating a candidate method for the determination of Na‐VP in human plasma with reasonable recovery and efficiency.