A Potentiometric Sensor for Cd2+ Based on Carbon Nanotube Paste Electrode Constructed from Room Temperature Ionic Liquid,Ionophore and Silica Nanoparticles

A novel and effective potentiometric sensor for the rapid determination of Cd²⁺ based on carbon paste electrode consisting of the room temperature ionic liquid 1‐butyl‐3‐methylimidazolium hexafluorophosphate, multiwalled carbon nanotubes, silica nanoparticles and ionophore was constructed. The prepared composite has a low potential drift, high selectivity and fast response time, which leads to a more stable potential signal. A linear dynamic range of 4.50×10^?9–1.00×10^?1 mol L^?1 with a detection limit of 2.00×10^?9 mol L^?1 was obtained. The modified electrode was successfully applied to the accurate determination of trace amounts of Cd²⁺ in environmental and biological samples.     

Molecularly imprinted polymer in microextraction by packed sorbent for the simultaneous determination of local anesthetics: lidocaine,ropivacaine, mepivacaine and bupivacaine in plasma and urine samples

This study presents the use of molecularly imprinted polymer (MIP) as packing material for microextraction by packed syringe (MEPS) to achieve higher extraction selectivity. Pentycaine was used as template for MIP. Development and validation of the determination of lidocaine, ropivacaine, mepivacaine and bupivacaine in human plasma and urine samples utilizing MIP‐MEPS and liquid chromatography–tandem mass spectrometry (LC‐MS/MS) were carried out. The MEPS MIP‐cartridge could be used for 100 extractions before it was discarded. The extraction recovery ranged from 60 to 80%. The correlation coefficients values were >0.999 for all assays using lidocaine, ropivacaine, mepivacaine and bupivacaine in the calibration range 5–2000 nmol/L. The accuracy of the studied compounds, given as a percentage variation from the nominal concentration values, ranged from ‐4.9 to 8.4% using plasma and urine samples. The between‐batch precision, given as the relative standard deviation, at three different concentrations (quality control samples) was ranged from ?4.7 to 14.0% and from 1.8 to 12.7% in plasma and urine, respectively. The lower limit of quantification and limit of detection of the studied substances were 5.0 and 1.0 nm , respectively. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis of coprecipitated strontium hexaferrite nanoparticles in the presence of polyvinyl alcohol

Strontium hexaferrite (SrFe₁₂O₁₉) nanoparticles were synthesized by the chemical coprecipitation method and using polyvinyl alcohol (PVA) as a protective agent. The synthesized samples were characterized by differential thermal analysis, X-ray diffraction, scanning and transmission electron microscopy, particle size analyzer, sedimentation test and vibrating sample magnetometer. In the presence of PVA, the single-phase SrFe₁₂O₁₉ nanoparticles were obtained at low temperature of 650 °C. The average particle size of SrFe₁₂O₁₉ precursor was 15 nm, which increased to 61 nm after calcination at 650 °C. The magnetic measurements indicated that PVA decreased coercivity from 4711 to 3216 Oe with particle size reduction. The results showed that PVA as a protective agent could be effective in decreasing the particle size, calcination temperature and coercivity of SrFe₁₂O₁₉ nanoparticles.     

Semi-automated cloud point extraction with cold column trapping of surfactant-rich phase for phenazopyridine determination in human serum

A semi-automated cold column trapping-cloud point extraction (CCT-CPE) method was developed and applied to the determination of phenazopyridine in human serum. In the proposed technique, a mixture of sample (pH 8) and Triton X-100 (0.4 % v/v) was incubated at 90 °C for 5 min in a heating sample cell. The developed turbid solution was then flowed through a CCT preconcentration column packed with C18 sorbent using a peristaltic pump. A pair of thermal electric cooler (TEC) plates was used for cooling the column. The surfactant-rich phase was retained on the CCT at 0 °C and desorbed, subsequently, in an elevated temperature by ethanol. The analytical parameters such as pH, surfactant concentration, temperature and incubation time were optimized by a central composite design (response surface) method. Six replicated analyses at the optimized conditions resulted in a recovery of 99.7 % and a relative standard deviation of 2.45 for phenazopyridine. The detection limit of the method (3σ) was 0.50 mg L^?1 for the analyte. Compared to conventional CPE, the proposed CCT-CPE method required less sample handling, eliminated the centrifugation step and was substantially faster. The method was successfully applied to the determination of phenazopyridine in some human serum and tablet samples.     

Polyaniline-Supported Zinc Oxide (ZnO) Nanoparticles: An Active and Stable Heterogeneous Catalyst for the Friedel–Crafts Acylation Reaction

We report herein the synthesis of zinc oxide (ZnO) nanoparticles incorporating a polyaniline (PANI) matrix in aqueous medium and its catalytic performance toward Friedel–Crafts acylation reactions. The acylation reactions demonstrate that polyaniline/nano-ZnO composites are very active catalysts and are able to activate the reactant at ambient temperature. The obtained nanocatalyst was characterized by Fourier transform–infrared, scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller, X-ray diffraction, and particle-size analysis techniques. The catalyst was reusable for five cycles without appreciable loss in activity.     

One‐Pot Synthesis of Sulfonamides and Sulfonyl Azides from Thiols using Chloramine‐T

A convenient synthesis of sulfonamides and sulfonyl azides from thiols is described. In situ preparation of sulfonyl chlorides from thiols was accomplished by oxidation with chloramine‐T (=N‐chlorotosylamide=N‐chloro‐4‐methylbenzenesulfonamide), tetrabutylammonium chloride (Bu₄NCl), and H₂O. The sulfonyl chlorides were then further allowed to react with excess amine or NaN₃ in the same pot.     

A numerical method for solving optimal control problems using state parametrization

A numerical method for solving a special class of optimal control problems is given. The solution is based on state parametrization as a polynomial with unknown coefficients. This converts the problem to a non-linear optimization problem. To facilitate the computation of optimal coefficients, an improved iterative method is suggested. Convergence of this iterative method and its implementation for numerical examples are also given.     

One step synthesis of 14-alkyl- or aryl-14H-dibenzo[a,j]xanthenes using sodium hydrogen sulfate as catalyst

A simple and environmentally benign procedure for the synthesis of 14-alkyl- or aryl-14H-dibenzo[a,j]xanthenes is described through a one-pot condensation of 2-naphthol with aryl or alkyl aldehydes in the presence of sodium hydrogen sulfate as a catalyst under solvent-free conditions.     

Flow invariance for solutions to nonlinear nonautonomous partial differential delay equations

We investigate the problem of existence and flow invariance of mild solutions to nonautonomous partial differential delay equations , t?s, us=φ, where B(t) is a family of nonlinear multivalued, α-accretive operators with D(B(t)) possibly depending on t, and the operators F(t,.) being defined—and Lipschitz continuous—possibly only on “thin” subsets of the initial history space E. The results are applied to population dynamics models. We also study the asymptotic behavior of solutions to this equation. Our analysis will be based on the evolution operator associated to the equation in the initial history space E.