Electrodeposition of Ag nanoparticles on graphenized pencil lead electrode as a sensitive and low-cost sensor for iodate determination

In this study, a simple, sensitive and low-cost iodate electrochemical sensor based on graphenized pencil lead electrode (GPLE) modified with Ag nanoparticles (AgNPs) was presented. The GPLE was simply prepared via electrochemical exfoliation of pencil lead electrode (PLE) by applying an optimized potential in acidic media. Afterward, silver nanoparticles were electrochemically deposited on the surface of GPLE using chronoamperometry technique. The fabricated electrode was carefully characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) techniques. Electrochemical behavior and also the electrocatalytic performance of the modified electrode toward the reduction of iodate were studied in details using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The fabricated sensor responds efficiently to iodate over the concentration range of 0.05 to 75 mM with a detection limit of 0.017 mM and sensitivity of 0.26 µA µM^?1 cm^?2. Remarkably enhanced electrocatalytic performance of the modified electrode was ascribed to the synergistic effect of graphene-like nanostructures with high surface to volume ratio, excellent conductivity and also the excessive electrocatalytic behavior of silver nanoparticles. The modified electrode was successfully employed for the determination of iodate in table and sea salt samples.     

Electronic reflectance spectra of palladium-on-alumina catalysts

The electronic reflectance spectra of palladium-on-alumina catalysts prepared by various procedures from different precursor compounds are discussed. Information is obtained about the chemical state of palladium in the individual steps of preparation.

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On the index of caterpillars

The index of a graph is the largest eigenvalue of its adjacency matrix. Among the trees with a fixed order and diameter, a graph with the maximal index is a caterpillar. In the set of caterpillars with a fixed order and diameter, or with a fixed degree sequence, we identify those whose index is maximal.     

Measuring the critical energy release rate in mode II of tough,structural adhesive joints using the tapered end-notched flexure (TENF) test

This paper shows and discusses results of the Tapered End-Notched Flexure (TENF) test, investigating the fracture behaviour of high-strength structural adhesive joints under shear loading. The TENF test has been previously applied to brittle joints by different authors and has been re-designed to be applicable to ductile adhesives in the presented work. Furthermore, the tests are performed at two velocities, a quasi-static and a dynamic one, to investigate rate effects on the fracture behaviour of the joint. All experimental work has been performed using the structural adhesive DOW Betamate 1496V.     

A Simple Stability Indicating CZE Method for the Analysis of Octreotide Acetate

A simple stability indicating capillary zone electrophoretic method was developed and validated for the analysis of octreotide acetate (OCT-Ac). The best separation was achieved by bare fused silica capillaries (50 μm i.d.; 65.5 cm total and 57.0 cm effective length), phosphate buffer (pH = 3.25; 50 mM), at 32.5 °C. The samples were injected using 50 mbar for 5 s and subjected to the applied voltage of 27.5 kV for separation. The detection was carried out using a PAD at a wavelength of 195 nm. For improving the repeatability of the method, l-histidine was applied as an internal standard. According to the validation results, the method was linear in the concentration range of 3.30–400 μg mL^?1 (correlation coefficient of 0.9996) with a limit of detection of 1.08 μg mL^?1 and a limit of quantification of 3.30 μg mL^?1; accuracy of the method was between 100.4 ± 0.2 and 101.1 ± 0.2 %; intra-assay precision was 0.5–2.6 % and intermediate precision was 1.3–3.2 %. The proposed method was successfully applied for the quantification of OCT-Ac in both a pharmaceutical formulation and force-degraded samples and for the detection and separation of degradation products; besides, the obtained results were used for the evaluation of the degradation kinetics of OCT-Ac under different stress conditions. So, it is concluded that the developed method could be employed as a simple, accurate and precise stability-indicating method in quality control laboratories to assess the quantity and stability of OCT-Ac pharmaceutical products.     

Expedient Catalytic Access to Knöevenagel Condensation Using Sr<Subscript>3</Subscript>Al<Subscript>2</Subscript>O<Subscript>6</Subscript> Nanocomposite in Room Temperature

Sr₃Al₂O₆ nanocomposite was prepared by sol gel method using aluminum isopropoxide, strontium nitrate, acetylacetone and polyethylene glycol as template, followed by calcination at 900 °C. This nanocomposite was characterized by various techniques including X-ray powder diffraction, infrared spectroscopy, elemental analysis, scanning transmission microscope and transmission electron microscope. It was found that Sr₃Al₂O₆ nanocomposite successfully catalyzes the Knöevenagel condensation of aromatic aldehydes with malononitrile in room temperature in ethanol. Expedient access to the corresponding Knöevenagel adducts in moderate to high yields within 6 min is promising. The recovered catalyst was reused for three times without significant loss of activity.     

The potential of the capillary electrophoresis techniques for quality control of biopharmaceuticals—A review

CE is considered as a powerful technique in biopharmaceutical industry, owing to its inherent advantages such as high resolution, efficient separation, and its flexibility to couple with high‐sensitive detecting methods. Present review provides a summary of the applications of CE‐based methods in the quality control of biopharmaceuticals according to the papers published between 1994 and July 2014. This article is divided into the sections based on different CE modes applied in the analysis of biopharmaceuticals and gives detailed information about the employed experimental conditions. At the end some overall conclusions and perspectives are given.