Highly selective thiocyanate poly(vinyl chloride) membrane electrode based on a cadmium–Schiff’s base complex

A PVC membrane electrode based on a cadmium–salen (N,N′-bis-salicylidene-1,2ethylenediamine) complex as an anion carrier is described. The electrode has an anti-Hofmeister selectivity sequence with a preference for thiocyanate at pH 1.5–11.0. It has a linear response to thiocyanate from 1.0 × 10^–6 to 1.0 × 10^–1 mol L^–1 with a slope of 59.1 ± 0.2 mV per decade, and a detection limit of 7 × 10^–7 mol L^–1. This electrode has high selectivity for thiocyanate relative to many common organic and inorganic anions. The proposed sensor has a fast response time of approximately 15 s. It was applied to the determination of thiocyanate in a milk sample. Received: 1 December 2000 / Revised: 19 April 2001 / Accepted: 30 April 2001     

Photocatalytic Activity of Supported Metal Nanoparticles and Single Atoms

Photocatalysis has been known as one of the promising technologies due to its eco-friendly nature. However, the potential application of many photocatalysts is limited owing to their large bandgaps and inefficient use of the solar spectrum. One strategy to overcome this problem is to combine the advantages of heteroatom-containing supports with active metal centers to accurately adjust the structural parameters. Metal nanoparticles (MNPs) and single atom catalysts (SACs) are excellent candidates due to their distinctive coordination environment which enhances photocatalytic activity. Metal-organic frameworks (MOFs), covalent organic frameworks (COFs) and carbon nitride (g-C₃N₄) have shown great potential as catalyst support for SACs and MNPs. The numerous combinations of organic linkers with various heteroatoms and metal ions provide unique structural characteristics to achieve advanced materials. This review describes the recent advancement of the modified MOFs, COFs and g-C₃N₄ with SACs and NPs for enhanced photocatalytic applications with emphasis on environmental remediation.     

One-pot synthesis of 2-amino-3-cyanopyridines and hexahydroquinolines using eggshell-based nano-magnetic solid acid catalyst via anomeric-based oxidation

Research on Chemical Intermediates - In the present research, the eggshell as a hazardous waste by European Union regulations was converted to a valuable catalyst, namely nano-Fe3O4@(HSO4)2. The...     

Synthesis of a new oxime and its application to the construction of a highly selective and sensitive Co(II) PVC-based membrane sensor.

A cobalt(II) ion-selective membrane sensor has been fabricated from a poly vinyl chloride (PVC) matrix membrane containing a new oxime compound (oxime of 1-(2-oxocyclohexyl)-1,2-cyclohexanediol, OXCCD) as a neutral carrier, sodium tetraphenyl borate (NaTPB) as an anionic excluder and o-nitrophenyloctylether (o-NPOE) as a plasticizing solvent mediator. The membrane sensor exhibits a linear potential response in the concentration range of 1.0 x 10(-1) - 1.0 x 10(-6) M of Co2+. The electrode displays a Nernstian slope of 29.8 mV decade(-1) in the pH range of 3.5 - 8.0. The sensor also exhibits a fast response time of < 25 s. The detection limit of the proposed sensor is 9.0 x 10(-7) M (approximately 40 ng/ml), and it can be used over a period of two months. The selectivity of the sensor with respect to other cations (alkali, alkaline earth, transition and heavy metal ions) is excellent. The practical utility of the sensor has been demonstrated by using it as an indicator electrode in the potentiometric titration of Co2+ with EDTA and for the direct determination of Co(II) in wastewater of the electroplating industry.     

Hydrophobic Deep Eutectic Solvents in Developing Microextraction Methods Based on Solidification of Floating Drop: Application to the Trace HPLC/FLD Determination of PAHs

In this work, we evaluated the applicability of hydrophobic carboxylic acid-based deep eutectic solvents (DESs) as environmentally friendly alternatives to common organic solvents in microextraction methods based on solidification of floating drop (SFD). Due to the limited number of solvents that can be used in SFD, the introduction of new solvents can help in the development of these attractive methods. Deep eutectic solvents consisting of tetra-n-butyl ammonium bromide (TBAB) and carboxylic acids were prepared and used as extraction solvent. They had the desirable characteristics such as low density, suitable freezing point and proper hydrophobicity which make them suitable alternatives to conventional organic solvents for SFD. With the help of the synthesized hydrophobic DESs, a simple, fast, efficient and environmentally friendly microextraction method was developed based on solidification of deep eutectic solvent (SFDES) without using any organic solvent. The proposed organic solvent-less microextraction method based on SFDES was applied in the analysis of polycyclic aromatic hydrocarbons (PAHs) as model compounds in environmental water samples. By coupling this method with high-performance liquid chromatography–fluorescence detection, we achieved low LOD values which is a necessity in the ultra-trace analysis of PAHs in environmental water samples. Under the optimized conditions, good linearity and low limits of detection of 0.7–6.6 ng L^?1 were obtained. The analysis of six PAHs in real water samples gave acceptable relative recoveries ranging from 83 to 117% with 5.4–10.5% intra-day relative standard deviations (RSD) and 4–7.1% interday RSD.

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Novel sulfate ion-selective polymeric membrane electrode based on a derivative of pyrilium perchlorate

A sulfate ion-selective PVC membrane sensor based on 4-(4-bromophenyl)-2,6-diphenylpyrilium perchlorate (BDPP) as a novel sensing material is successfully developed. The electrode shows a good selectivity for sulfate ion with respect to common organic and inorganic anions. The sensor exhibits a good linear response with slope of -28.9+/-0.5 mV per decade over the concentration range of 1.0x10(-6)-1.0x10(-2) M, and a detection limit of 8.0x10(-7) M of SO(4)(2-) ions. The electrode response is independent of pH in the range of 4.0-9.0. The proposed sensor was applied as an indicator electrode in potentiometric titration of sulfate and barium ions, and to the determination of zinc in zinc sulfate tablets.     

Rapid and Efficient Synthesis of Imidazolines and Bisimidazolines Under Microwave and Ultrasonic Irradiation

Summary. Small assemblies of 2-imidazolines and bisimidazolines from appropriate nitriles and ethylenediamine with catalytic amounts of P₂S₅ employing a microwave assisted protocol were prepared. Sonication of this system also led to successful synthesis of 2-imidazolines and bisimidazolines. Another advantage of these systems is the ability to carry out large scale reactions.     

Study of the plasma equilibrium in Damavand tokamak via numerical solution of the Grad-Shafranov equation

In this work we study the Damavand tokamak plasma equilibrium with an elongated ross section and fixed boundary conditions. These equilibria are characterized by three parameters such as elongation, triangularity and magnetic axis shift. An iterative scheme f the moment’s method is used to solve the Grad-Shafranov equation in flux coordinate system. Magnetic flux surface contours and main equilibrium parameters have been btained by applying the geometry and boundary conditions of the Damavand tokamak.