Capillary electrophoresis of quantum dots: Minireview

It has been already three decades, since the fluorescent nanocrystals called quantum dots (QDs) appeared and attracted attention of a broad scientific community. Their excellent not only optical but also electronic properties predetermined QDs for utilization in a variety of areas. Besides lasers, solar cells, and/or computers, QDs have established themselves in the field of (bio)chemical labeling as well as medical imaging. However, due to the numerous application possibilities of QDs, there are high demands on their properties that need to be precisely controlled and characterized. CE with its versatile modes and possibilities of detection was found to be an effective tool not only for characterization of QDs size and/or surface properties but also for monitoring of their interactions with other molecules of interest. In this minireview, we are giving short insight in analysis of QDs by CE, and summarizing the advantages of this method for QDs characterization.     

Pd black decorated by Pt sub-monolayers as an electrocatalyst for the HCOOH oxidation

Pd black was modified by a very low amount of Pt corresponding to a sub-monolayer (ML). Spontaneous displacement method was employed. The catalysts with 0.02–0.12 ML were characterized by cyclic voltammetry and CO_ads stripping and were tested for HCOOH oxidation under the potentiodynamic and potentiostatic conditions. All the Pt@Pd catalysts were more active for HCOOH oxidation than Pd black. The Pt@Pd with 0.08 ML of Pt exhibited the highest activity with the maximum current density under the potentiodynamic conditions of 8 mA cm^?2 (vs. 2.7 mA cm^?2 on Pd black). Contrasting HCOOH oxidation kinetics on Pt@Pd and Pt@Au catalysts revealed that the current densities are higher, and the poisoning rate is lower on Pt@Pd catalyst. This was ascribed to an optimal strength of the Pt–adsorbate bond when Pt is supported on Pd and to a possible influence of the Pt atoms on the Pd substrate.     

Experimental verification of the modified Gran methods applicable to redox systems

This study describes the application of the modified Gran I and II methods for determination of equivalence volume in redox titrations and for calibration, i.e. for determination of the correct slope of the redox indicator electrodes, which appears to be a major problem in using these electrodes. The four new versions of the Gran II method, denoted as MG(II)B, MG(II)C, MG(II)D and MG(II)E methods, in which the problem of calibration and determination of equivalence volume are considered simultaneously are suggested and compared with MG(I)S and MG(II)A methods known hitherto. All the methods are experimentally tested and discussed.     

Complexation of uranium(VI) with aromatic acids in aqueous solution: a combined computational and experimental study

The complexes of uranium(VI) with salicylhydroxamate, benzohydroxamate, and benzoate have been investigated in a combined computational and experimental study using density functional theory methods and extended X-ray absorption fine structure spectroscopy, respectively. The calculated molecular structures, relative stabilities, as well as excitation spectra from time-dependent density functional theory calculations are in good agreement with experimental data. Furthermore, these calculations allow the identification of the coordinating atoms in the uranium(VI)-salicylhydroxamate complex, i.e. salicylhydroxamate binds to the uranyl ion via the hydroxamic acid oxygen atoms and not via the phenolic oxygen and the nitrogen atom. Carefully addressing solvation effects has been found to be necessary to bring in line computational and experimental structures, as well as excitation spectra.     

On Jordan Triple Derivations and Related Mappings

In this article we study certain functional equations and systems of functional equations related to (generalized) derivations on semiprime rings. In particular, we prove that any generalized Jordan triple derivation on a 2- torsion free semiprime ring is a generalized derivation. We also prove that any (generalized) Jordan triple *-derivation on a 2-torsion free semiprime *-ring is a (generalized) Jordan *-derivation. The second author was supported in part by the Ministry of Science, Education and Sports of the Republic of Croatia (project No. 037-0372784-2757).     

Automated Solid-Phase Oligo(disulfide) Synthesis

A method for automated solid-phase synthesis of oligo(disulfide)s was developed. It is based on a synthetic cycle comprising removal of a protecting group from a resin-bound thiol followed by treatment with monomers containing a thiosulfonate as an activated precursor. For ease of purification and characterization, the disulfide oligomers were synthesized as extensions of oligonucleotides on an automated oligonucleotide synthesizer. Six different dithiol monomer building blocks were synthesized. Sequence-defined oligomers of up to seven disulfide units were synthesized and purified. The sequence of the oligomer was confirmed by tandem MS/MS analysis. One of the monomers contains a coumarin cargo that can be released by a thiol-mediated release mechanism. When the monomer was incorporated into an oligo(disulfide) and subjected to reducing conditions, the cargo was released under near-physiological conditions, which underlines the potential use of these molecules in drug delivery systems.     

Characterization and quantitative analysis of surfactants in textile wastewater by liquid chromatography/quadrupole-time-of-flight mass spectrometry

A method based on the application of ultra-performance liquid chromatography (UPLC) coupled to hybrid quadrupole-time-of-flight mass spectrometry (QqTOF-MS) with an electrospray (ESI) interface has been developed for the screening and confirmation of several anionic and non-ionic surfactants: linear alkylbenzenesulfonates (LAS), alkylsulfate (AS), alkylethersulfate (AES), dihexyl sulfosuccinate (DHSS), alcohol ethoxylates (AEOs), coconut diethanolamide (CDEA), nonylphenol ethoxylates (NPEOs), and their degradation products (nonylphenol carboxylate (NPEC), octylphenol carboxylate (OPEC), 4-nonylphenol (NP), 4-octylphenol (OP) and NPEO sulfate (NPEO-SO4). The developed methodology permits reliable quantification combined with a high accuracy confirmation based on the accurate mass of the (de)protonated molecules in the TOFMS mode. For further confirmation of the identity of the detected compounds the QqTOF mode was used. Accurate masses of product ions obtained by performing collision-induced dissociation (CID) of the (de)protonated molecules of parent compounds were matched with the ions obtained for a standard solution. The method was applied for the quantitative analysis and high accuracy confirmation of surfactants in complex mixtures in effluents from the textile industry. Positive identification of the target compounds was based on accurate mass measurement of the base peak, at least one product ion and the LC retention time of the analyte compared with that of a standard. The most frequently surfactants found in these textile effluents were NPEO and NPEO-SO4 in concentrations ranging from 0.93 to 5.68 mg/L for NPEO and 0.06 to 4.30 mg/L for NPEO-SO4. AEOs were also identified.     

Interplay of thermochemistry and <Emphasis Type="Italic">Structural Chemistry</Emphasis>, the journal (volume 18, 2007) and the discipline

In this study, we relate the contents of the journal Structural Chemistry for the calendar year 2007 and thermochemistry. The year’s articles were briefly summarized and a thermochemical comment written to supplement them. Frequently questions were asked and future research was suggested.     

Influence of interfacial water layer on surface properties of silver halides: effect of pH on the isoelectric point

The hypothesis that pH dependent charge of interfacial water affects electrokinetic charge and electrokinetic potential of hydrophobic colloids, but not the (inner) surface potential was tested. It was found that isoelectric points of silver chloride, bromide and iodide shift to the higher pAg values in the acidic solutions, but that surface potential did not depend on pH. Isoelectric points of water at inert surfaces lie in the range 2相似文献   

Fast and universal HPLC method for determination of permethrin in formulations using 1.8-μm particle-packed column and performance comparison with other column types

An HPLC method has been developed for the fast separation and quantification of permethrin using C18 column packed with 1.8 μm particles. The method is specific with good resolution to degradation products and to other present components. It has acceptable validation results. The run time is 4.5 min (or may be within 1.6 min is rapid resolution mode) with an organic solvent consumption of 3.6 mL per run. The method has been applied to samples of formulations for various uses: mattress cleaner, shampoo, and veterinary powder. The performance of the applied column is compared with other common column types. The relationships between linear velocity of the mobile phase (u) and resolution factor (Rs), back-pressure (ΔP), and efficiency (H) are presented. The experimental data shows the advantages of 1.8-μm particle columns to be a significant reduction in solvent consumption (by factor of 4.4 and 1.5) and a reduction in run-time (by factor 4.7 and 1.5), and the weaknesses are a high back-pressure and lower efficiency. Finally, it has been shown that use of 1.8-μm particle packed columns with conventional HPLC systems is possible, but with limitations in mobile phase flow-rate.