Electrochemical characterization of core@shell CoFe2O4/Au composite

Quantum dots (QDs) have received considerable attention due to their unique optical and electrical properties. Although substantial research has focused on the potential applications and toxicological impacts of QDs, far less effort has been directed toward understanding their fate and transport in the environment. In this work, the effect of four coatings, polyethylene glycol functionalized polymer (PEGP), carboxyl derivatized polymer (COOHP), linoleic acid (LA), and polyacrylic acid-octylamine (PAA-OA), on the transport and retention of QDs in porous media were evaluated under environmentally relevant conditions. Aqueous QD suspensions (ca. 10 nM) were introduced into water-saturated columns packed with 40–50 mesh Ottawa sand at a pore-water velocity of 7.6 m/day. At an ionic strength (IS) of 3 mM and pH of 7, PEGP-coated QDs were completely retained within the column, while more than 60 % of COOHP-coated QDs were transported through a column run under identical conditions. When PAA-OA and LA were used as coatings, effluent QD recoveries increased to more than 65 and 89 % of the injected mass, respectively. Additionally, a decrease in pH from 9.5 to 5.0, or an increase of IS from 0 to 30 mM reduced the eluted mass of PAA-OA-coated QDs by more than 2 and 15 times, respectively. The relative mobility of coated QDs (LA > PAA-OA > COOHP > PEGP) was consistent with total interaction energy profiles between QDs and sand surfaces calculated based on Derjaguin–Landau–Verwey–Overbeek (DLVO) theory. At an IS of 3 mM (NaCl) and pH 7, a linear correlation was obtained between the fraction of eluted QDs and the magnitude of the primary interaction energy barrier. These findings demonstrate the strong dependence of QD transport on coating type and indicate that interaction energies based on DLVO theory can be used to predict the relative mobility of QDs in porous media.     

Determination of trace bismuth by under-potential deposition-stripping voltammetry at mesoporous platinum microelectrodes: application to pharmaceutical products

A methodology for the determination of bismuth, based on under-potential deposition-stripping voltammetry (UPD-SV), was investigated. It makes use of mesoporous platinum microelectrodes (Pt-MEs) prepared by a liquid crystal templating technique. The mesoporous microelectrodes, which are characterised by a very high surface area, allowed the accumulation of relatively large amounts of bismuth at under-potential without saturation of the electrode surface. Calibration plots for quantification of bismuth at micromolar levels were constructed by using the charge involved in either the anodic or cathodic peak recoded by cyclic voltammetry that ensued the accumulation of bismuth at the electrode surface. During the anodic scan, the oxidation of metallic bismuth occurred; the cathodic scan involved irreversibly adsorbed bismuth species, which are retained on to the electrode surface. The reproducibility of the proposed UPD-SV procedure (which was within 5 %) was assured by the application to the Pt-MEs of a suitable potential waveform, properly designed to avoid memory effect due to the irreversibly deposited bismuth. The latter phenomenon along with UPD allowed to overcome interference due to copper, which is normally observed when quantification of bismuth is performed by anodic stripping voltammetry at solid electrodes involving bulk metal deposits. The usefulness of the proposed method for the determination of bismuth in real samples was demonstrated by the analysis of a tablet of a pharmaceutical preparation, which is used for curing ulcers.     

Small Targeted Cytotoxics: Current State and Promises from DNA‐Encoded Chemical Libraries

The targeted delivery of potent cytotoxic agents has emerged as a promising strategy for the treatment of cancer and other serious conditions. Traditionally, antibodies against markers of disease have been used as drug‐delivery vehicles. More recently, lower molecular weight ligands have been proposed for the generation of a novel class of targeted cytotoxics with improved properties. Advances in this field crucially rely on efficient methods for the identification and optimization of organic molecules capable of high‐affinity binding and selective recognition of target proteins. The advent of DNA‐encoded chemical libraries allows the construction and screening of compound collections of unprecedented size. In this Review, we survey developments in the field of small ligand‐based targeted cytotoxics and show how innovative library technologies will help develop the drugs of the future.     

In-syringe magnetic-stirring-assisted liquid–liquid microextraction for the spectrophotometric determination of Cr(VI) in waters

A fully automated method for the determination of chromate is described. It is based on the selective reaction of Cr(VI) with diphenylcarbazide in acidic media to form a colored complex of Cr(III) with the oxidation product diphenylcarbazone. The reaction was performed within the syringe of an automatic burette containing a magnetic stirrer for homogenization of the sample and the required reagents. In-syringe stirring was made possible using a specially designed driving device placed around the syringe barrel to achieve a rotating magnetic field in the syringe, forcing the stirrer to spin. In a second step, the reaction mixture in the syringe was neutralized to allow in-syringe magnetic-stirring-assisted dispersive liquid–liquid microextraction of the complex into 125 μL of n-hexanol. After phase separation by droplet flotation over 30 s, the organic phase was propelled into a coupled spectrophotometric detection cell. The entire multistep procedure including in-system standard preparation was done within 270 s. The method was used for the analysis of natural waters, achieving average analyte recovery of 103 %, a limit of detection of 0.26 μg L^-1, and a repeatability of less than 4 % relative standard deviation.     

Determination of the two major endocannabinoids in human plasma by μ-SPE followed by HPLC-MS/MS

Endocannabinoids (ECs) are endogenous compounds that interact with type-1 and type-2 cannabinoid receptors (CB₁ and CB₂), as well as non-cannabinoid receptors. The multitude of roles attributed to ECs makes them an emerging target of pharmacotherapy for a number of disparate diseases. Here a high-throughput bioanalytical method based on micro SPE (μ-SPE) followed by LC-MS/MS analysis for the simultaneous determination of the two major endocannabinoids 2-arachidonoylglycerol (2-AG) and N-arachidonoylethanolamine (anandamide, AEA) in human plasma is presented. The chromatographic conditions obtained with the fused-core column allowed a good separation in 10 min also of the AG isomers. A very simple and reliable extraction has been optimised by means of C18-modified tips: it requires only 100 μL of plasma and allows the use of minimal volumes of organic solvent. The present method allows a rapid and effective clean-up, which also minimises the isomerisation of 2-AG. The whole procedure has been validated following the FDA guidelines for bioanalytical methods validation: the satisfactory recovery values, the negligible matrix effect and the good values of accuracy and reproducibility make it a simple and high-throughput analytical tool for clinical and biochemical studies on endocannabinoid signaling in humans.

Electronuclear multiconfiguration time‐dependent hartree calculations on the confined H atom with mobile electron and nucleus

A multiconfiguration time‐dependent Hartree method oriented toward calculations of a non‐Born‐Oppenheimer nature has been applied to the calculation of the dynamical properties of a confined H atom. The calculation is fully six‐dimensional and does not take into account constraints arising from linear or angular momentum conservation. The orbital evolution is monitored and the energy level spectrum of the system, as well as the dependence of the results on the decomposition of the Hamiltonian and on the correlation between radial degrees of freedom, is determined. © 2012 Wiley Periodicals, Inc.     

Some Applications of Isopropenyl Acetate To O-, N-and C-Acetylation

New procedures for the preparation of drugs and drug intermediates (isosorbide-5-nitrate, diltiazem) and intermediates of potential drugs using isopropenyl acetate are described.     

The Effect of Gluconate and EDTA on Thorium Solubility Under Simulated Cement Porewater Conditions

α-Hydroxy carboxylate ligands like gluconate or polyaminocarboxylate ligands such as ethylenediaminetetraacetate (EDTA) are frequently used in decontamination procedures at nuclear power plants. The presence of these organic substances among nuclear wastes could enhance the solubility of actinides by forming soluble complexes. Thermodynamic data on the stability of gluconate and EDTA with actinides are essential to predict their increase in mobility, especially in high pH systems characteristic of cement environments of a nuclear waste repository. In this work, the solubility of thorium oxyhydroxide in the presence of gluconate and EDTA has been studied. The results highlight the key role of these organics in increasing the solubility of thorium at pH_c = 12. The presence of calcium at concentrations below 10^?2 mol·dm^?3 (characteristic of cement porewaters corresponding to cement compositions at the second degradation stage) does not seem to affect significantly the thorium solubility under the studied conditions.