Speciation Analysis of Cr(III) and Cr(VI) after Solid Phase Extraction Using Modified Magnetite Nanoparticles

A new solid phase extraction (SPE) method has been developed for the speciation of Cr(III) and Cr(VI). This method is based on the adsorption of Cr(VI) on modified alumina‐coated magnetite nanoparticles (ACMNPs). Total chromium in different samples was determined as Cr(VI) after oxidation of Cr(III) to Cr(VI) using H₂O₂. The chromium concentration has been determined by flame atomic absorption spectrometric (FAAS) technique and amount of Cr(III) was calculated by substracting the concentration of Cr(VI) from total chromium concentration. The effect of parameters such as pH, amount of adsorbent, contact time, sample volume, eluent type, H₂O₂ concentration and cetyltrimethylammonium bromide (CTAB) concentration as modifier on the quantitative recovery of Cr(VI) were investigated. Under the optimal experimental conditions, the preconcentration factor, detection limit, linear range and relative standard deviation (RSD) of Cr(VI) were 140 (for 350 mL of sample solution), 0.083 ng mL^?1, 0.1‐10.0 ng mL^?1 and 4.6% (for 5.0 ng mL^?1, n = 7), respectively. This method avoided the time‐consuming column‐passing process of loading large volume samples in traditional SPE through the rapid isolation of CTAB@ACMNPs with an adscititious magnet. The proposed method was successfully applied to the determination and speciation of chromium in different water and wastewater samples and suitable recoveries were obtained.     

Silica‐Bound 3‐{2‐[Poly(ethylene Glycol)]ethyl}‐Substituted 1‐Methyl‐1H‐imidazol‐3‐ium Bromide: A Recoverable Phase‐Transfer Catalyst for Smooth and Regioselective Conversion of Oxiranes to β‐Hydroxynitriles in Water

A series of β‐hydroxynitriles were efficiently synthesized from the regioselective ring opening of oxiranes by cyanide anion in the presence of silica‐bound 3‐{2‐[poly(ethylene glycol)]ethyl}‐substituted 1‐methyl‐1H‐imidazol‐3‐ium bromide (SiO₂? PEG? ImBr) as a novel recoverable phase‐transfer catalyst in H₂O (Scheme 1 and Table 2). The workup procedure was straightforward, and the catalyst could be reused over four times with almost no loss of catalytic activity and selectivity.     

Electrochemical Synthesis of Polypyrrole in the Presence of Congo Red; Application to Selective Voltammetric Determination of Dopamine in the Presence of Ascorbic Acid

The electrosynthesis of polypyrrole (PPy) film has been achieved on glassy carbon electrode (GCE) in aqueous medium of Congo red (CR) by means of cyclic voltammetry (CV). The modified electrode exhibits high electrocatalytic activity toward dopamine (DA) oxidation, with drastic enhancement of the reversibility and peak currents. This modified electrode, due to electrostatic interactions, is capable to mask the response of ascorbic acid (AA) completely and provide an effective method for the detection of minor amounts of dopamine in the presence of high concentrations of AA. The electrochemical response of the film modified electrode is strongly dependent to the switching potential applied in the CV procedure of the electro‐polymerization. The results show that by increasing the switching potential more than 0.75 V, the peak of AA is gradually disappeared. This peak in potential of 0.85 V is reached to capacitive background current. With respect to the destruction of the conjugated structure of ppy and lowering the conductivity of the film at the surface of modified electrode, higher switching potentials cannot be suitable for electropolymerization procedure. The effects of various experimental parameters such as, number of polymerization cycles, switching potential, pH and potential sweep rate on the voltammetric response of dopamine were also investigated. The modified electrode shows a linear response to DA in the range of 0.5 to 100 μM with a detection limit of 0.1 μM. The prepared modified electrode does not show any considerable response toward sulfhydryl compounds, such as, cysteine, penicillamine and glutathione, revealing a good selectivity for voltammetric response to DA. The effective electrocatalytic property, ability for masking the voltammetric responses of the other biological reducing agents together with high reproducibility and stability make the modified electrode suitable for selective and sensitive voltammetric detection of sub‐micromolar amounts of DA in clinical and pharmaceutical preparations.     

Intrinsic equations for a generalized relaxed elastic line on an oriented surface in the galilean space

In this article, we derive the intrinsic equations for a generalized relaxed elastic line on an oriented surface in the Galilean 3-dimensional space G₃. These equations will give direct and more geometric approach to questions concerning about generalized relaxed elastic lines on an oriented surface in G₃.     

Green Regioselective Azidolysis of Epoxides Catalyzed by Multi‐Site Phase‐Transfer Catalyst

A facile synthesis of 1,2‐azidoalcohols from their epoxides using α,α',α”‐N‐hexakis(triethylammoniummethylene chloride)‐melamine as a multi‐site phase‐transfer catalyst in water was developed. By this eco‐friendly and highly atom‐economic method, a variety of 1,2‐azidoalcohols was obtained in high yields with excellent regioselectivity and in short reaction times. Application of this six‐site PTC in the ring opening of epoxides by cyanide, acetate and chloride anions was also studied. The catalyst can be recovered after completion of the reaction and can be recycled without affecting the catalytic property.     

Lentivirus-mediated transgene delivery to the hippocampus reveals sub-field specific differences in expression

Background  

In the adult hippocampus, the granule cell layer of the dentate gyrus is a heterogeneous structure formed by neurons of different ages, morphologies and electrophysiological properties. Retroviral vectors have been extensively used to transduce cells of the granule cell layer and study their inherent properties in an intact brain environment. In addition, lentivirus-based vectors have been used to deliver transgenes to replicative and non-replicative cells as well, such as post mitotic neurons of the CNS. However, only few studies have been dedicated to address the applicability of these widespread used vectors to hippocampal cells in vivo. Therefore, the aim of this study was to extensively characterize the cell types that are effectively transduced in vivo by VSVg-pseudotyped lentivirus-based vectors in the hippocampus dentate gyrus.