Some applications of proton-induced X-ray emission spectrometry in the elemental analysis of metallurgical materials

Summary A proton-induced X-ray emission (PIXE) procedure for the determination of iron, chromium and tin in zircaloy, zirconium in pure hafnium, and yttrium in titanium alloy has been proposed. After suitable acid dissolution of the samples, aliquots were deposited onto membrane filters and irradiated by a 2.5-MeV proton beam from a cyclotron or a Van de Graaff accelerator. Calibration was achieved making use of the standard addition method. Preliminary separations are not required and the PIXE results have been well compared with those obtained by other accepted methods of analysis. Precision, accuracy and limits of detection for the elements of interest are discussed. The results demonstrate the feasibility of PIXE as an alternative analytical technique for metallurgical materials.

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Anwendung der protonen-induzierten Röntgenemissions-Spektrometrie (PIXE) zur Elementanalyse metallurgischer Materialien

Zusammenfassung Ein PIXE-Verfahren zur Bestimmung von Fe, Cr und Sn in Zircaloy, von Zr in reinem Hafnium und von Y in Titanlegierung wird beschrieben. Nach entsprechender Lösung der Probe in Säure wird ein aliquoter Teil auf einem Membranfilter niedergeschlagen und mit 2,5-MeV-Protonen bestrahlt (Cyclotron oder Van-de-Graaff-Beschleuniger). Eichung erfolgt mit Hilfe des Standardzugabe-Verfahrens. Vortrennungen sind nicht erforderlich. Die Ergebnisse lassen sich gut mit denen anderer Verfahren vergleichen. Präzision, Genauigkeit und Nachweisgrenzen werden diskutiert. Die Resultate bestätigen die Brauchbarkeit des PIXE-Verfahrens zur Analyse metallurgischer Materialien.

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Research Associate of the National Fund for Scientific Research (Belgium)     

Some applications of conformational analysis in organic chemistry

Part 1 of this account deals with the conformational analysis of the diastereomers of RCHXCHXR (R=CH₃, X=Cl, Br; R=C₆H₅ X=Br) and of compounds of the type R₂CHCHR₂ and RR′CHCHRR′ (R and R′ alkyl). These studies are closely related to Mizushima's pioneering work. In part 2, conformational equilibria of geminally substituted phenylcyclohexanes are discussed, including that of phencyclidine [1-phenyl-1(N-piperidino)cyclohexane] as a function of solvent, temperature and protonation and that of the chromium tricarbonyl complexes of phenylcyclohexane and of 1-methyl-1-phenylcyclohexane.     

Some applications of thermal analysis to fullerenes

Thermal analysis is a convenient means of characterizing the soot used as a source of the carbon clusters, the extracted mixture of fullerenes, and the individual clusters themselves. TG in an inert atmosphere will rapidly assay the volatile fractions, presumably the lower molecular weight clusters. TG in oxygen indicates — a slight weight gain for the soots and clusters prior to their combustion.DSC in oxygen is used to determine the heat of combustion for the separated C₆₀ and C₇₀ materials. The combustion occurs around 300°C for the clusters. There is a small exothermic peak before this which is attributed to the oxidation associated with the slight weight gain. The heats of combustion measured are –18.7 and –21.0 kJ·mol^–1 for the C₆₀ and C₇₀ respectively.MS-EGA indicates the loss of small amounts of water and argon at temperatures around 250°C in vacuum and of solvent at about 350°C prior to sublimation.

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Zusammenfassung Thermoanalyse ist ein praktisches Hilfsmittel zur Charakterisierung von Ruß als Quelle für Kohlenstoffcluster, extrahierte Gemische von Fullerenen und die individuellen Cluster an sich. TG in einer inerten Atmosphäre ergibt schnell die flüchtigen Fraktionen, wahrscheinlich die niedermolekularen Cluster. TG in Sauerstoff zeigt einen leichten Gewichtszuwachs für Ruß und Cluster vor ihrer Zersetzung.DSC in Sauerstoff wurde angewendet, um die Verbrennungswärme der getrennten C₆₀ und C₇₀ Materialien zu ermitteln. Die Verbrennung erfolgt für die Cluster bei etwa 300°C. Davor kann ein kleiner exothermer Peak beobachtet werden, welcher der Oxidation in Verbindung mit dem geringen Gewichtszuwachs zugeschrieben wird. Die gemessenen Verbrennungswärmen betragen –18.7 und –21.0 kJ·mol^–1 für C₆₀ bzw. C₇₀.MS-EGA zeigt den Verlust von geringen Mengen an Wasser und Argon bei Temperaturen von etwa 250°C in Vakuum und von Lösungsmittel bei etwa 350°C, bevor die Sublimation eintritt.

     

Inorganic polarography in organic solvents-I Some metal-pyridine-thiocyanate complexes in toluene

Results are reported for the direct application of polarography to the examination of organic phases following solvent extraction. Experimental factors such as suitable solvents, supporting electrolytes and electrode parameters have been studied and the method is tested for the extraction of the Cd, Co(II), Cu(II), Fe(II), Mn(II), Ni and Zn pyridine/thiocyanate complexes into toluene. The results show that the sensitivity is increased by the concentrating effect of the extraction system and better selectivity is achieved without searching for a suitable supporting electrolyte.     

Some applications of enthalpimetric detection in flow injection analysis

Summary A flow injection manifold is described based on a flow-through arrangement of thermistors for measuring heat effects of chemical reactions. Temperature changes down to 10^–3 °C can be measured reproducibly. The working range for the determination of a component is dependent on the reaction enthalpy and can vary from 10^–3 to 10 mol/l for acids and bases, from 10 to 1000 ppm for e.g., alkylhydroperoxides. Sample frequencies up to 150 samples per hour can be realized.

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Einige Anwendungen der enthalpimetrischen Detektion in der Fließinjektionsanalyse

     

Current examples of practical and fundamental applications of DC polarography

Examples of recent applications—applied, analytical, and fundamental are given. For these types of applications, an understanding of at least the number of electrons and protons transferred and the sequences of electron transfers and chemical reactions is essential. Polarography can be used for the determination of the active component in tablets and injection solutions, where it offers speed and sensitivity of the analytical method. Electroactive species can also be determined in heterogeneous systems without pre-separation. This has been taken advantage of in the investigation of reactions of bile salts with heavy metal ions or of binding of pesticides and other toxins on lignin. Polarography can also be used in the investigation of alkaline cleavage of lignin under mild conditions. Kinetics of this cleavage was used as a tool in proving that humic acids are not natural products. Among fundamental applications belong proofs of limited delocalization in groupings >C=N–N=C<, of diprotonation of hydrazones and oximes at the electrode surface, as well as of formation of imines as intermediates in reductions of hydrazones and oximes. Simultaneous determination of benzaldehyde and its hydrazone enabled providing experimental evidence for formation of carbinolamines as reaction intermediates and interpretation of the pH dependence of the equilibrium constant of this reaction. Differences in hydration of three isomeric phthalaldehydes are discussed as well as the covalent hydration of 1,2,4- and 1,3,5-triazines and pyrimidines. The ω,ω,ω-trifluoroacetophenone oxime the C=N bond is covalently hydrated.Dedicated to Professor Dr. Alan Bond on the occasion of his 60th birthday.     

Inorganic polarography in organic solvents-III Analytical applications of metal-acetylacetonate complexes in toluene

Indium and palladium are determined polarographically with a dropping mercury electrode in a toluene phase, following extraction as the acetylacetonates from aqueous solutions containing 2-10 ppm of the metals (or 0.1-0.5 ppm with a greater ratio of sample volume to solvent volume). Of 31 elements examined, only Co(III), Cr(III), Cu(II), Fe(III), In, Mo(VI), Pd and Ti(IV) gave extractable complexes with reduction waves in the available potential range. Specificity for palladium is obtained by extraction at pH 0.5, and for indium at pH 9 m the presence of cyanide and ascorbic acid as masking agents.     

Some applications of thermal methods of analysis to polymers

Some examples are given of the application of thermogravimetry, differential scanning calorimetry, thermomechanical analysis, torsional braid analysis, stress relaxometry and dynamic viscoelastometry to the study of cross-linked polymer systems. The information derived by the use of each technique is outlined and the advantages and disadvantages of the different methods are compared.

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Zusammenfassung Einige Beispiele der Anwendung der Thermogravimetrie, Differential Scanning Kalorimetrie, thermomechanischen Analyse, Torsionsfadenanalyse, Streßrelaxometrie und dynamischen Viscoelastometrie zur Untersuchung quervernetzter Polymersysteme werden gegeben. Die an Hand des Einsatzes der einzelnen Techniken erhaltenen Informationen werden beschrieben und die Vor- und Nachteile der verschiedenen Methoden miteinander verglichen.

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Résumé On donne quelques exemples de l'application de la thermogravimétrie, de l'analyse calorimétrique différentielle (DSC), de l'analyse thermomécanique, de l'analyse au fil de torsion, de la mesure de la relaxation des tensions, de la viscoélastométrie dynamiques, à l'étude des polymères à réseau tri-dimensionnel. On souligne les renseignements obtenus en utilisant chacune de ces techniques et on compare les avantages et les inconvénients de ces différentes méthodes.

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Some applications of thermal analysis to the coordination chemistry

The behaviour of complexes of the type MeD2I2 (Me=Co,D = acetylacetone or benzoylacetone,I = imidazole and derivatives in the course of the stepwise thermal degradation is different. In the case ofD = acetylacetone in the first step acetylacetone is split off. At D = benzoylacetone the decomposition starts with the partial elimination of the heterocyclic ligands.In-position unsubstituted nickelacyclic complexes from type (bipy)Ni(CH₂CH₂CH₂COO) decompose by a reductive elimination and separating of CO₂ forming a (bipy)Ni-intermediate. A single reductive decoupling is hindered by blocking up the-position.Opposite to the high thermal stability of the trimesityl aluminium the intermediates Almes₂Cl and AlmesCl₂ show with decreasing amounts of mesityl groups and increasing content of halogene, respectively, a significant decreasing thermal stability.The thermal degradation of nickelchelates of alkylsubstituted chinolin-8-ol starts with the dehydration followed by a different separation of the ligands as a function of the chain-length and the position of the substituents of the ligands.

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Zusammenfassung Das Zersetzung Verhalten der Komplexverbindungen vom Typ C0D2I2 (P = acetylaceton, Benzoylaceton;I = Imidazol oder Derivate) erfolgt stufenweise. Im Falle vonD = Acetylaceton erfolgt zuerst eine Eliminierung von Acetylaceton wärend beiD = Benzoylaceton zuerst ein Heteroligand eine Abspaltung erfährt.Bei einer unsubstituierten-Position von Nickelacyclen des Typs (bipy)Ni(CH₂CH₂CH₂COO) erfolgt eine thermisch induzierte-Hydrideliminierung unter Ringspaltung und Freisetzung von CO₂.Im Gegensatz zur hohen thermischen Stabilität des Trimesityl Aluminium erfahren die Zwischenverbindungen Almes₂Cl und AlmesCl₂ mit abnehmenden Mesityl- bzw. zunehmenden Chlorgehalt einen wessentlich früheren thermischen Zerfall. Bei zunehmenden Kovalenzgrad ist hier ein Einfluss der veränderten Polarisation anzunehmen.Der thermische Abbau der prinzipiell wasserhaltig kristallisierenden Nickelchelate von alkylsubstituierten Chinolin-8-ol beginnt jeweils mit der Dehydratisierung. In Abhängigkeit von der Kettenlänge und der Position der Substitution am Chinolin schliesst sich der thermische Abbau der Chelatliganden ein- bzw. mehrstufig an.

     

Some methods and applications of electron density distribution analysis

Accurate and efficient integration of the electron density function over arbitrary regions has been previously achieved by exploiting a separation of variables. Recently, a computer program has been written that calculates ρ, \documentclass{article}\pagestyle{empty}\begin{document}$ \buildrel{\rightharpoonup}\over{\nabla} $\end{document}ρ, and ?²ρ in an expeditious fashion, taking advantage of the separation of variables in the electron density function. Accurate integrations of ?²ρ over arbitrary regions can also be accomplished. The structure of the program is suited especially to vector processors. As a result of the efficiencies of these programs, functions of the electron density, such as the density itself, the surrounding electrostatic potential, ?ρ, and ?²ρ have been calculated in three dimensions. Results of calculations for nitrated cubanes are presented illustrating how the effects of the nitro groups are manifested in the electron density and associated properties.     

Applications of polarography and voltametry in analysis for drugs

Recent developments and applications of polarographic and voltammetric techniques in drug analysis are reviewed. Typical applications to pharmacologically active compounds are described.     

Methodology of multicriteria optimization in chemical analysis Some applications in stripping voltammetry

Multicriteria optimization, widely used in engineering, does not much used in the optimization of analytical signals. The aim of this paper is to show the usefulness of the desirability function to optimize instrumental responses obtained in instrumental analysis. The simultaneous optimization of a signal and of its variability is a generic question of interest to any chemical analyst. It is clear that the improvement of the two responses forms the basis of the validation of any analytical method, and affects all the figures of merit: accuracy (trueness and precision), capability of detection, robustness, sensitivity, etc. Furthermore, in the specific case of electroanalysis, an improvement in the signal may implicitly mean an increase of the signal in the blank, such that the “net signal” may not improve. This experimental approach (surface response methodology plus desirability) to multicriteria optimization has been applied to three cases of growing complexity. Thus, in the determination of Cu(II) by differential pulse anodic stripping voltammetry the simultaneous maximization of the peak current and minimization of its standard deviation is looked for. Whereas, in the determinations of Ni(II) and indomethacin by differential pulse adsorptive stripping voltammetry, the simultaneous maximization of the peak current and minimization of the blank signal is desired. In all the cases, the experimental conditions where the optima are found for each individual response are just opposite, so it is required to look for a certain compromise, that is achieved using the desirability function.