Determination of trace level impurities in uranium compounds by ICP-AES after organic extraction

The determination was studied of Al, B, Be, Cd, Ca, Co, Cu, Mg, Mn, Mo, Pb, Si, Sn, V, Cr, Ni, and Fe as trace level impurities in uranium compounds by ICP-AES after extraction of uranium with three different mixtures of di-(2-ethyl-hexyl) phosphate (D2EHP) and tri-(2-ethyl-hexyl)-phosphate (T2EHP) in solvents like toluene, carbon tetrachloride, hexane and cyclohexane. The study was carried out in presence of different concentrations of HCl and HNO₃. A single extraction with D2EHP in cyclohexane using nitric acid as matrix was sufficient to reduce the U₃O₈ concentration from 100 g/l to 100 g/ml. The ICP-AES instrumentation applied, allowed the determination of metal concentrations ten-times lower than those usually found in nuclear grade U₃O₈. To check the efficiency of the extraction and the accuracy of the proposed method, Certified Reference Materials were used in the dissolution and extraction steps. The method described can be used for the determination of trace metals in nuclear grade U₃O₈.     

Kinetic study of the thermal dehydration of layered [Ni2Al(OH)6]2SO4.nH 2O

The kinetics of thermal dehydration of [Ni₂Al(OH)₆]₂SO₄.nH₂O has been studied through the analysis of isothermal weight loss data. The results obtained seem to indicate that the process is governed by a diffusion mechanism up to an value which is dependent on the temperature. An explanation is provided for this behaviour on the basis of the structural properties of the compound and the nature of the water loss.

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Zusammenfassung Die Kinetik der thermischen Dehydratisierung von [Ni₂Al(OH)₆]₂SO₄.nH₂O wurde mittels isothermer TG untersucht. Die Ergebnisse scheinen darauf hinzudeuten, daß der Prozeß bis zu einem von der Temperatur abhängigen -Wert von einem Diffusionsmechanismus bestimmt wird. Für dieses Verhalten wird basierend auf den strukturellen Eigenschaften der Verbindung und der Natur der Wasserabgabe eine Erklärung gegeben.

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, [Ni₂Al(OH)₆]₂SO₄.nH₂O. , , . , .

     

Surface chemistry of InP quantum dots: a comprehensive study

Advanced (1)H, (13)C, and (31)P solution and solid-state NMR studies combined with IR spectroscopy were used to probe, at the molecular scale, the composition and the surface chemistry of indium phosphide (InP) quantum dots (QDs) prepared via a non-coordinating solvent strategy. This nanomaterial can be described as a core-multishell object: an InP core, with a zinc blende bulk structure, is surrounded first by a partially oxidized surface shell, which is itself surrounded by an organic coating. This organic passivating layer is composed, in the first coordination sphere, of tightly bound palmitate ligands which display two different bonding modes. A second coordination sphere includes an unexpected dialkyl ketone and residual long-chain non-coordinating solvents (ODE and its isomers) which interact through weak intermolecular bonds with the alkyl chains of the carboxylate ligands. We show that this ketone is formed during the synthesis process via a decarboxylative coupling route and provides oxidative conditions which are responsible for the oxidation of the InP core surface. This phenomenon has a significant impact on the photoluminescence properties of the as-synthesized QDs and probably accounts for the failure of further growth of the InP core.     

The Fluorophore 4′,6‐Diamidino‐2‐phenylindole (DAPI) Induces DNA Folding in Long Double‐Stranded DNA

DAPI (4′,6‐diamidino‐2‐phenylindole) is a widely used fluorescent dye, whose complicated binding features to DNAs and RNAs have been the object of debates and are still not fully understood. In this study, different approaches were employed, including binding equilibrium measurements (spectrofluorometry), melting experiments (spectrophotometry), viscometric measurements, circular dichroism, and T‐jump kinetic analyses; all data concur in shedding light on the complex mechanistic aspects of the binding mode of DAPI to natural DNA. Conditions are found that induce the mode of the DAPI/DNA interaction to change from groove binding to intercalation. Moreover, it is observed, for the first time, that DAPI is able to induce the formation of a rather compact polymer–dye adduct under particular conditions. The results suggest that this form is a folded or coiled DNA structure stabilized by DAPI dye bridges.     

Specific features of rubber recovery from latex with poly-N,N-dimethyl-N,N-diallylammonium chloride in the presence of cotton fiber

The effect of cotton fiber additions on the coagulating power of a cationic polyelectrolyte, poly-N,N-dimethyl-N,N-diallylammonium chloride, in rubber recovery from SKS-30 ARK latex was studied. The influence of the coagulating agent dosage and coagulation temperature on the completeness of the rubber recovery, with the polyelectrolyte introduced in the presence of cotton fiber and without it, was examined.     

On a Correlation between the Results of In-Hospital Analysis of Biosamples from Children Performed Using Standard Methods and an Array of Piezosensors

Journal of Analytical Chemistry - A rapid procedure for obtaining information on changes in particular characteristics of urine as the most frequently taken biosample is presented. The relationship...     

Determination of lead in the presence of morin-5′-sulfonic acid and sodium dodecyl sulfate by adsorptive stripping voltammetry

A simple and sensitive electroanalytical method is developed for the determination of lead by adsorptive stripping voltammetry (AdSV) in the presence of morin-5′-sulfonic acid (MSA) and sodium dodecyl sulfate (SDS). The Pb-MSA complex accumulates on the surface of a hanging mercury drop electrode (HMDE) and peak current is measured by square wave voltammetry (SWV). The complex is reduced at −0.48 V and peak current increases when low concentrations of SDS are added to the sample solution. The experimental variables pH, MSA concentration (C_MSA); accumulation time (t_acc); accumulation potential (E_acc), and SDS concentration (C_SDS), as well as potential interferences, are investigated. Under the optimized conditions (pH 3.2; C_MSA: 0.5 μmol L⁻¹; t_acc: 60 s; E_acc: −0.35 V, and C_SDS: 20 μmol L⁻¹), peak current is proportional to the concentration of Pb(II) over the 0.1-32.0 μg L⁻¹ range, with a detection limit of 0.04 μg L⁻¹. The relative standard deviation for a solution containing 5.0 μg L⁻¹ of Pb(II) solution was 1.5% for seven successive assays. The method was validated by determining Pb(II) in synthetic sea water (ASTM D665) spiked with ICP multi-element standard solution and in certified reference water (GBW08607). Finally, the method was successfully applied to the determination of Pb(II) in tap water and sea water after UV digestion.