Tandem on-line continuous separation and determination of arsenic by inductively coupled plasma atomic emission spectrometry

The principle of tandem on-line continuous separation techniques as an alternative means of introducing samples into plasmas was applied to the development of a sensitive, selective and convenient method for the determination of arsenic by inductively coupled plasma atomic emission spectrometry (ICP-AES). Arsenic is continuously extracted as AsI₃ into xylene from the sample dissolved in 0.1 M potassium iodide solution in 7.2 M hydrochloric acid. The xylene phase (containing the analyte) is continuously mixed on-line with NaBH₄ in dimethylformamide and acetic acid solutions. Arsine is thus continuously generated directly from the organic phase and is separated in a gas—liquid separation device which prevents most of the xylene phase vapour from reaching the ICP. The system was optimized for the continuous extraction of AsI₃, the direct generation of arsine from xylene and the final ICP determination of arsenic. Finally, the tandem on-line continuous separation ICP detection system was applied to the determination of arsenic in real samples (white metal, cast iron, cupro-nickel and orchard leaves standard materials). Very good agreement between the experimental results and the certified values was obtained.     

Representation des courbes de vaporus dans les systemes binaires a tension de vapeur non negligeable

The binary system As₂Se₃-As is first described for a constant value of the specific volumeV/m. The results corroborate the data given by other authors. The system is then described by aT-V-x diagram, by using DTA and electron microprobe analysis. From our experimental results and from the literature crystallographic and vapour pressure data, aT-V-x phase diagram was set up, showing the vaporus curves and the eutectic, peritectic and peritectoid invariant planes.

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Zusammenfassung Das binäre System As₂Se₃-As wird zunächst für einen konstanten Wert des specizifischen VolumensV/m beschrieben. Die Ergebnisse bestätigen die Daten anderer Autoren. Danach wird das System imT-V-x-Diagramm beschrieben, wobei DTA und Elektronenmikroproben-Analyse angewandt werden. Von eigenen Versuchsergebnissen und der Literatur entnommenen kristallographischen und Dampfdruckdaten wurden dasT-V-x-Phasendiagramm aufgestellt, das die Dampfdruckkurven und die eutektischen, peritektischen und peritektoiden invarianten Flächen zeigt.

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As₂Se₃-As V/m. , , , T-V-x. , , T-V-x., , , .

     

New type of blue ternary complex of arsenazo I with plutonium (IV) in the presence of hydrogen peroxide: preliminary investigations

The preparation and spectrophotometric properties of a new type of complex compound of arsenazo I with Pu(IV) in the presence of H₂O₂ are described. The new compound has a blue colour, derived from a wide absorption band with a maximum at 610 nm. and a corresponding molar absorptivity of 4 × 10⁴ l. mole⁻¹.cm⁻¹. From 2 hr after its preparation this curious new compound undergoes for several days a steady decomposition accompanied by decolorization. The formation of similar peroxy Pu(IV) complexes has not so far been shown to take place with arsenazo III or with any other “arsenazo-type” reagent.     

Kinetics and mechanism of substitution reactions of complexes,XX

Thermal decomposition of 21 complexes of the type [Co(DH)₂(amine)₂]NCS has been studied under the conditions of thermogravimetric analysis, by using different heating rates. From the thermogravimetric curves apparent kinetic parameters of the pyrolysis reaction have been derived by means of the modified Doyle method. Apparent reaction order increases and apparent activation energy decreases with increasing heating rate. Thus, the obtained kinetic parameters do not characterize the purely chemical reaction, but the complex heterogeneous process as a whole. The explanation of the observed effect is discussed. Results are compared with those obtained with other analogous complexes.

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Zusammenfassung Die thermische Zersetzung von 21 Komplexen des Typs [Co(DH)₂(Amin)₂]NCS wurde thermogravimetrisch bei verschiedenen Aufheizungsgeschwindigkeiten untersucht. Aus den TG-Kurven wurden die scheinbaren kinetischen Parameter der Reaktion mit Hilfe der Doyleschen Methode ermittelt. Bei zunehmender Aufheizungsgeschwindigkeit wächst die scheinbare Reaktionsordnung während die scheinbare Aktivierungsenergie abnimmt. Die erhaltenen chemischen Parameter kennzeichnen nicht die eigentliche chemische Reaktion, sondern den ganzen komplexen heterogenen Vorgang. Die beobachteten Effekte wurden diskutiert und die Ergebnisse verglichen mit Resultaten von Untersuchungen anderer analoger Komplexe.

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Résumé On a étudié par thermogravimétrie, avec différentes vitesses d'échauffement, la décomposition thermique de 21 complexes du type [Co(DH)₂(amine)₂SCN. On a calculé suivant la méthode deDoyle les paramètres cinétiques apparents déduits des courbes d'ATG. L'ordre apparent de la réaction augmente si la vitesse d'échauffement croît, alors que l'énergie d'activation apparente décroît. Les paramètres cinétiques obtenus ne caractérisent que le processus hétérogène complexe et non la réaction chimique proprement dite. Les effets observés ont été discutés et comparés avec les résultats obtenus avec d'autres complexes analogues.

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21 [(D)₂()₂]NS , . . . , , . . , .

     

Effective interactions in the colloidal suspensions from hypernetted-chain theory

The hypernetted-chain (HNC) Ornstein-Zernike integral equations are used to determine the properties of simple models of colloidal solutions where the colloids and ions are immersed in a solvent considered as a dielectric continuum and have a size ratio equal to 80 and a charge ratio varying between 1 and 4000. At an infinite dilution of colloids, the effective interactions between colloids and ions are determined for ionic concentrations ranging from 0.001 to 0.1 mol/l and compared to those derived from the Poisson-Boltzmann theory. At finite concentrations, we discuss on the basis of the HNC results the possibility of an unambiguous definition of the effective interactions between the colloidal molecules.     

Etude de la séparation du thorium d'avec les terres cériques

Résumé Nous avons étudié les complexes que forment les acides éthylèneglycolbis-(-aminoéthyléther)] Sr,N-tétracétique et ,-diaminodiéthylétherN,N-tétracétique, soit avec le thorium, soit avec les terres cériques et, à la suite de cette étude, nous avons pu établir une méthode d'analyse et une séparation du thorium d'avec les terres cériques qui nous a donné satisfaction.

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Summary A study has been conducted of the complexes formed by the ethyleneglycol-bis (-amino-ethylether)-N,N-tetraacetic acid and,-diaminodiethylether-N,N-tetraacetic acid with either thorium or the ceric earths. As a result of this investigation, it was possible to set up a method of analysis and a separation of thorium from the cerium earths. These procedures have proved satisfactory.

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Zusammenfassung Die von Äthylenglykol-bis-(-aminoäthyläther)-N,N-tetraessigsäure bzw.von ,-Diaminodiäthyläther-N,N-tetraessigsäure mit Thorium bzw. mit den Cer-Erden gebildeten Komplexe wurden untersucht. Auf Grund der Ergebnisse konnte ein Analysenverfahren und eine Trennungsmethode für Thorium und Cer-Erden entwickelt werden.

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Une communication de ce travail a été faite à Graz, lors de la commémoration du centenaire de la naissance deF. Emich.     

Planar defects in β-alumina

Sodium β-alumina crystals were elaborated by melting of a mixture of Na₂CO₃ and Al₂O₃ or by PbO flux evaporation and were studied by transmission electron microscopy. They exhibit regular planar defects lying in the {11.0} prismatic planes. These defects are described as antiphase boundaries for the cationic sublattice with fault vectors $\text{1}\text{2}\text{〈10.0〉}$ (such faults do not affect the anionic sublattice). As a consequence it would be interesting to study precisely the structure of the sodium β cationic lattice in the vicinity of the melting point.     

Trace crossings in cyclic voltammetry and electrochemic electrochemical inducement of chemical reactions: Aromatic nucleophilic substitution

Crossing of anodic and cathodic traces is frequently observed on cyclic voltammograms featuring the electrochemical induction of a chemical reaction in the case where the product standard potential is positive to the reactant reduction potential. The theory of this phenomenon has been established in the contaxt of aromatic nucleophilic substitution. The reaction of potassium diethyl phosphite on 4-chlorobenzonitrile in liquid ammonia was investigated as an example illustrating this type of phenomenon and its interpretation. The simulation of the experimental voltammograms demonstrates the proposed mechanistic and kinetic model and allows the rate constants of the various steps to be determined. Much higher rate constants can thus been attained than by the standard application of electrochemical techniques (the gain may reach five or six orders of magnitude). A procedure is derived from these observations and then a rationalization for inducing chemical reactions with a very low electricity consumption as opposed to that which occurs when the electrode potential is settled at the level of the reactant wave.     

Exploiting C3-symmetry in the dynamic coordination of a chiral trisoxazoline to copper(II): improved enantioselectivity, and catalyst stability in asymmetric lewis acid catalysis

Chiral C3-symmetric trisoxazolines are highly efficient stereodirecting ligands in enantioselective Cu(II) Lewis acid catalysis which is based on the concept of a stereoelectronic hemilability of the divalent copper; in direct comparison with the analogous bisoxazoline systems they are more efficient in the enantioselective alpha-amination as well as the enantioselective Mannich reaction of prochiral beta-ketoesters.     

Rapid separation of phenylthiohydantoin amino acids: ambient pressure ion-mobility mass spectrometry (IMMS)

An electrospray ionization (ESI) ambient pressure ion-mobility spectrometer (APIMS) interfaced to an orthogonal reflector time-of-flight mass spectrometer (TOFMS) was evaluated for the first time as a detector for the identification of phenylthiohydantoin (PTH)-derivatized amino acids, the final products in the Edman sequencing process of peptides and proteins. The drift and flight times of the twenty common PTH amino acids were characterized by a well-defined 2-D mobility/mass spectral pattern. The combination of mobility/mass modes of analysis gave rise to a unique trend-line formation for the series of PTH amino acids. In addition, each PTH amino acid had a unique reduced mobility constant K(o), thus enabling the differentiation of all the amino acid derivatives including the PTH-leucine and PTH-isoleucine isomers. More importantly it was shown that it was possible to resolve a complete reference mixture of PTH amino acids in a single experimental run in less than 1 min. Detection limits for the PTH amino acids were found to range from 1.04 to 3.52 ng; indicating that the limits of detection were less than 17.0 pmol for all of the PTH amino acids.