Ultrasensitive Simultaneous Quantification of Nanomolar Level of Cd and Zn by Cathodic Adsorptive Stripping Voltammetry in Some Real Samples

A novel, simple and sensitive adsorptive stripping voltammetry method was developed for simultaneous determination of Cd and Zn using N‐Nitrozo‐N‐phenylhydroxylamine (Cupferron) as a selective complexing agent. Cadmium and zinc metals gave peaks that were distinctly separated by 450–1200 mV, allowing their determination over a wide range of concentrations. The influence of pH and the nature of supporting electrolytes, concentration of ligand, preconcentration time and applied potential were investigated. The detection limits were 0.058 ng/mL for Zn and 0.092 ng/mL for Cd, and the RSD at a concentration level of 50 ppb, were 1.8–2.1 % for both zinc and cadmium, respectively. The method was applied to the determination of cadmium and zinc in blood, drug, food and water samples with the satisfactory results.     

Modeling and optimizing of sonochemical degradation of Basic Blue 41 via response surface methodology

The nanocatalyst-assisted sonodegradation of Basic Blue 41 (BB41) dye in aqueous medium was modeled and optimized using response surface method (RSM) based on Box-Behnken design. The studied variables included pH, initial dye concentration, H₂O₂ concentration and sonolysis time while each factor varied at three levels: Low level (−1), Medium level (0) and High level (+1). The ultrasound -assisted degradation was well described by developing quadratic model with correlation value squared (R²) of 0.9114. Factor effects along with interaction effects were evaluated. The graphical optimization step was conducted to achieve the best experimental condition in dye removal. pH, H₂O₂ concentration and initial dye concentration of the reaction were investigated. It was recognized that at lower pH values the dye removal rate decreased. However, dye removal rate increased (82.5%) by increasing the concentration of H₂O₂ and by lowering the initial dye concentration.      

In vivo imaging of intrinsic optical signals in chicken retina with functional optical coherence tomography

Visually evoked intrinsic optical signals (IOSs) were measured in vivo for the first time to our knowledge from all retina layers of the chicken retina with a combined functional optical coherence tomography and electroretinography (ERG) system. IOS traces were recorded from a small volume in the retina with 3.5 μm axial resolution and 7 ms time resolution. Comparison of the IOS and ERG traces shows a correlation between the positive and negative IOS measured from different retinal layers and the timing of the a and b waves in the ERG recording.     

Variable viscosity effects on the peristaltic motion of a third‐order fluid

The effect of variable viscosity on the peristaltic motion of MHD third‐order fluid in a channel is studied using slip condition. The series solution for stream function, longitudinal velocity and pressure gradient are first derived and then discussed in detail. The pressure rise and frictional forces are monitored through numerical integration. Copyright © 2010 John Wiley & Sons, Ltd.     

Properties of poly(dimethylsiloxane)/hydrogel multicomponent systems

The properties of surface‐ and bulk‐modified poly(dimethylsiloxane) (PDMS) were examined. Laser‐induced surface grafting of poly(2‐hydroxyethyl methacrylate) (PHEMA) on PDMS and a sequential method for preparation of interpenetrating polymer networks of PDMS/PHEMA were, respectively, used for surface and bulk modifications. The hydrogel content and water‐uptake capability of the modified samples were also investigated. The modified PDMS samples were examined by performing attenuated total reflection/Fourier transform infrared spectroscopy, dynamic mechanical thermal analysis, scanning electron microscopy, and water contact‐angle measurements. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2145–2156, 2003     

Highly efficient synthesis of dicoumarols and xanthene derivatives in presence of Brønsted–Lewis acidic ionic liquids catalyst

A series of metal chloride-based acidic ionic liquids have been prepared and used as an efficient catalyst in one-pot multicomponent synthesis of biscoumarins and substituted xanthenes derivatives under solvent-free conditions. Among the acidic ionic liquids, N-methylpyrrolidonium zinc chloride (Hnmp/ZnCl₃)-based Brønsted–Lewis acidic ionic liquids were found to be an effective and recyclable catalyst for a one-pot synthesis of biscoumarins through the domino Knoevenagel–Michael reaction of a variety of aldehydes with 4-hydroxycoumarin in short reaction times. The reactions which occur under relatively mild conditions afforded the biscoumarin derivatives employing a very low loading of catalyst in satisfactory isolated yields and high purity after simple work-up. The Brønsted–Lewis acidic ionic liquid catalyst was reused four times without any variation in yield.     

One‐Pot Synthesis of New 1,5‐Disubstituted Tetrazoles Bearing 2,2‐Bis(trimethylsilyl)ethenyl Groups via The Ugi Four‐Component Condensation Reaction Catalyzed by MgBr2·2Et2O

A simple one‐pot Ugi four‐component condensation reaction has been developed for the synthesis of tetrazoles bearing 2,2‐bis(trimethylsilyl)ethenyl groups from the synthesized 4‐[2,2‐bis(trimethylsilyl) ethenyl]benzaldehyde ( 1 ), various amines, isocyanides, and trimethylsilylazide at room temperature, without solvent, and in the presence of catalytic amounts of MgBr₂·2Et₂O as catalyst.     

Structural studies of 3-chloro-N-(8′-quinolyl)×benzo[b]thiophene-2-carboxamide

3-Chloro-N-(8′-quinolyl)benzo[b]thiophene-2-carboxamide was synthesized from 3-chlorobenzo[b] thiophene -2-carboxyl chloride and 8-aminoquinoline in the presence of triethylamine. The single crystal X-ray structure determination confirmed the earlier proposed structure and also characterized by ¹HNMR, and Mass spectroscopy. Crystallographic study reveals that the structure crystallizes in monoclinic system, a = 14.878(4) ?, b = 8.4292(15) ?, c = 25.461(7) ?, β = 112.022(18)°, Z = 8, V = 2960.20(12) ?³ with space group C2/c (No. 15). In the structure packing, three kinds of interactions are responsible for the stability of the structure. Infinite two-dimensional stair-like layered chains are formed by relatively strong intermolecular hydrogen bonds [C14—H14...O1]. These parallel chains are connected by several π—π and CH—π interactions, alternatively. There are two such parallel chains with 70.53°, which are in contact by van der Waals interactions.     

Ultra Sensitive Quantification of Thiourea at Nanomolar Level by Catalytic‐Kinetic Differential Pulse Voltammetry

A new simple and highly selective and sensitive catalytic differential pulse voltammetry procedure for the determination of thiourea at nanomolar level is reported. Thiourea has a catalytic effect on the oxidation of Janus green by iodate in the hydrochloric acid medium. The potential was scanned in the negative direction and the differential pulse voltammograms were recorded. The variations of the peak current with hydrochloric acid concentration, oxidant, Janus green, pulse amplitude, pulse time and scan rate were optimized. Under the optimized conditions, the relationship between the peak current and concentration of thiourea was obtained. It is shown that the calibration curve is linear in the range of 0.01–6.00 µg/mL. The detection limit of the method was 0.005 µg/mL. The relative standard deviation for 6 replicate determinations of 0.01, 0.50 and 2.00 µg/mL is equal to 2.25%, 1.52% and 1.03%, respectively. The method was applied to the determination of thiourea in fruit juices with satisfactory results.