Heterogeneous hydride generation in a packed membrane cell

Summary Volatilization of arsenic, selenium and antimony for sample introduction in atomic absorption spectrometry has been performed by pumping an acidic sample through an anion exchanger in the tetrahydroborate (III) form packed as a bed in the liquid channel of a gas-liquid separation membrane cell. The hydrides generated in the heterogeneous reaction between bound tetrahydroborate (III) ions and the analytes are rapidly transferred with the aid of the concomitantly generated hydrogen gas through the gas-permeable membrane into the gas phase and swept to the spectrometer by an additional hydrogen gas flow. This instant transfer of the hydrides to the gas phase kinetically discriminates the reaction of the hydride with metal borides and metal colloids, whose formation by reaction with tetra-hydroborate (III) is slower than the hydride reaction. The susceptibility to interference by transition metal ions is thus markedly reduced, as compared with both batch hydride generation methods and a previously presented heterogeneous reaction scheme. The detection limits for arsenic, selenium, and antimony were 1.2, 3.7, and 10 g/l, respectively. The calibration graphs were linear from the detection limit up to 125 g/l for arsenic, 150 g/l for selenium, and 250 g/l for antimony. The relative standard deviations at concentration levels of 10 and 100 g/l were 1.8 and 0.7% for arsenic and 2.3 and 1.2% for selenium. Corresponding figures for 50 and 100 g/l antimony were 2.5 and 1.6%.     

Thermal analysis in the study of the new oxide-based superconductors

Thermoanalytical methods offer a convenient means for testing the starting materials used in the synthesis of the ceramic superconductors and for establishing the reaction and annealing temperatures as well as the stoichiometry of the end product. In addition, the stability and other thermal properties of the superconducting materials can be investigated including phase transformations during thermal cycling and possible reactions with substrates and the environment. The applications of TG, DSC/DTA and other thermal techniques for the study of the YBa₂Cu₃O_7–x superconductor are briefly reviewed using results from own experiments and selected literature data to illustrate the examples given.

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Zusammenfassung Thermoanalytische Methoden eignen sich zum Erproben von Ausgangsmaterialien zur Synthese von Keramiksupraleitern und zur Ermittlung der Reaktions- und Glühtemperaturen sowie der stöchiometrischen Zusammensetzung der Endprodukte. Außerdem können die Stabilität und andere thermische Eigenschaften der supraleitenden Materialien, einschließlich deren Phasenübergängen beim Wärmecycling sowie möglicher Reaktionen mit Substraten oder mit der Umwelt untersucht werden. Es wird kurz die Anwendung von TG-, DSC/DTA- und anderen thermischen Verfahren bei der Untersuchung des Supraleiters YBa₂Cu₃O_7–x beschrieben sowie Ergebnisse aus eigenen Experimenten un zur Illustration der aufgeführten Beispiele ausgewählte Literaturangaben gegeben.

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, , , . , , . , / YBa₂Cu₃O_7–x, , .

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This work has been supported by the Technology Development Centre (TEKES) through grant 4126/1988. The stimulating discussions and cooperation with Professor T. Katila and his group as well as Mr. K. Härkönen, M.Sc. are gratefully acknowledged. Mr. I. Danielsson from Oy Philips Ab is thanked for the permission to publish the high-temperature XRD pattern.     

Heat capacity of niobium chlorides in the range 6–320 K

The heat capacities of NbCl₅ and Nb₃Cl₈ samples with less than 1·10^–3 mass-% of impurities were determined over the range 6–320 K by an adiabatic calorimeter. An anomaly was found in Nb₃Cl₈ within the 7–13 K range. Comparisons ofC _p values of Nb₃Cl₈ are made with the theoretical works of Tarassov. The qualitative fit is quite good.

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Zusammenfassung Die Wärmekapazitäten von NbCl₅- und Nb₃Cl₈-Proben mit Verunreinigungsgehalten 10^–3 Masse-% wurden mit einem adiabatischen Kalorimeter bei 6 bis 320 K bestimmt. Am Nb₃Cl₈ wurde eine Anomalie bei 7 bis 13 K nachgewiesen. Die C_p-Werte von Nb₃Cl₈ werden mit theorischen Ergebnissen von Tarassov verglichen, die qualitative Übereinstimmung ist gut.

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6–320 NbCl₅ Nb₃Cl₈ , 1· 10^–3 . Nb₃Cl₃ 7–13 . _p Nb₃Cl₈ , .

     

Elements in car and truck tires and their volatilization upon incineration

The trace metal loading of used car and truck tires and the fractions of the metals volatilized upon incineration of the tire were determined. INAA was chosen due to its multielement analysis capability and its low detection limit for many elements. A high purity planar germanium detector was used. Among the elements measured were, Al (4–150 g/g), Ti (41–730 g/g), V (0.04–0.4g/g), Mg (>80–580 g/g), Zn (1–2.2%) as typical concentrations; also some amounts of antimony, bromine and arsenic have been found. Major differences in elemental concentrations have been observed between the tread and the wall of a tire, and also between different brands.     

Application of the photoionization detector for single determinations of hydride forming elements

The application of a photoionization detector in conjunction with a flow-through system is described for the determination of arsenic, antimony, selenium, tellurium, bismuth, tin, sulfide and ammonia. The analytical procedure is based upon a preliminary generation of the hydride compounds, their subsequent transfer to the gas phase and finally their detection in the photoionization detector. Linear calibration curves were obtained over three to four orders of magnitude with the following 3s-detection limits: 4 ng/ml As, 0.3 ng/ml Sb, 0.5 ng/ml Se, 3.0 ng/ml Te, 0.1 g/ml Bi, 0.5 g/ml Sn, 10.0 ng/ml S^2–, 0.5 g/ml NH₃.     

Untersuchungen zur Bestimmung von Spurenelementen in Blutserum mit Hilfe der Totalreflexions-R?ntgenfluoreszenzanalyse

Summary The quantitative determination of trace elements in human blood serum by Total Reflection X-Ray Fluorescence Analysis (TXRF) is influenced by absorption- and reflection-effects caused by the organic (proteins) and inorganic (P, S, Na, K, Ca, Cl) matrices. To minimize these effects we have developed a sample preparation technique based on the decomposition of the organic matrix and followed by the separation of the trace elements from the organic matrix by ion-exchange. The described method enables the simultaneous determination of K (1584 g), Ca (666 g), Fe (22 g), Cu (9.6 g), Zn (8.8 g), Se (0.97 g), Sn (1.3 g), Pb (0.12 g) and Rb (1.6 g) (obtained values in parentheses).

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Herrn Prof. Dr. G. Tölg zum 60. Geburtstag gewidmet     

Certified reference materials (CRM 408 and 409) for quality control of main components (ammonium, calcium, hydronium, magnesium, nitrate, potassium, sodium and sulphate) in simulated rain water

Analyses of rainwater are routinely performed by a number of organisations to monitor the contribution from rainwater to the component occurrences in the environment and the acidification of the environment. To control the quality of such determinations, the Community Bureau of Reference (BCR) has organised a certification campaign to produce two simulated rainwater reference materials (CRM 408, low mineral content and CRM 409, high mineral content). The materials were carefully prepared (addition of pro analysis and supra pure reagents with the mentioned elements to silica-free deionised water) and its homogeneity and long-term stability were verified. The materials were certified for their contents of ammonium (106 mol/kg) (CRM 409), calcium (7.68 and 15.5 mol/kg), chloride (67.3 and 113 mol/kg), hydronium (16.6 and 48.0 mol/kg), magnesium (6.14 and 12.3 mol/kg), nitrate (20.1 and 78.1 mol/kg), potassium (4.25 mol/kg) (CRM 409), sodium (42.0 and 82.9 mol/kg) and sulphate (10.5 and 53.2 mol/kg). Indicative values (not certified) are given for ammonium and potassium in CRM 408. This paper presents the certification work performed, as well as the analytical work for the certification of the contents of relevant species.     

Zur Verteilung von Dotierungsstoffen in Selengleichrichterplatten

Zusammenfassung Zur schichtweisen Analyse von Tellurmengen im ppm-Bereich in Selengleichrichterplatten wird das Selen mit wäßriger Alkalicyanidlösung in etwa 1 starken Schichten von diesen abgelöst. Für die Abtrennung der darin befindlichen Tellurspuren eignet sich die gemeinsame reduzierende Fällung durch Hydrazindichlorid mit Selen als Spurenfänger. Die quantitative Analyse des Tellurs erfolgt in Gegenwart eines maximal 10⁵fachen Selenüberschusses mit Hilfe der durch Chrom katalysierten Redoxreaktion zwischen Tellur(IV) und Tri-1, 10-eisen(III)-phenanthrolin (Ferriin). 20 Proben können in 2 Tagen analysiert werden. Es betragen die Standardabweichung im Bereich von 3–50 g Tellur etwa 0,6 g, der Streubereich für 99%ige Sicherheit ±42% resp. ±12%, die Erfassungsgrenze 1,5 g in 25 ml und die Grenzkonzentration 0,06 g/ml. Ein Beispiel für die Tellurverteilung in einer Selengleichrichterplatte ist wiedergegeben.

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On the distribution of doping elements in selenium rectifier cellsII. Method for the determination of the distribution of tellurium in selenium rectifier cells

The dissolution of the selenium in ca. 1 layers is realised by aqueous solutions of alkali cyanides. The separation of the ppm amounts of tellurium from this solution is possible in acid medium by a reducing coprecipitation of the traces of tellurium by hydrazine dichloride with selenium as trace catcher. In the presence of an excess up to 10⁵ of selenium tellurium is determined quantitatively by means of the Cr-catalysed redox reaction between tellur(IV) and tri-1,10-phenanthroline-iron(III) (ferriin). 20 samples can be completed in 2 days. The standard deviation in the range from 3 g to 50 g is about 0.6 g; the limit of error for 99% security is ±42%, respectively ±12%; the limit of detection is 1.5 g tellurium in 25 ml according to 0.06 g/ml. An example for the distribution of tellurium in a selenium rectifier cell is given.

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I. Mitteilung: D. Baresel u. K. Jaetsch: diese Z. 249, 234 (1970).

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Jetzt: Robert Bosch GmbH, Forschungsinstitut Berlin.

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Der Fa. Siemens AG danken wir für die Genehmigung zur Veröffentlichung der Ergebnisse, Herrn Dr. Iwantscheff und Herrn Ernst im Forschungszentrum der Siemens-Schuckert-Werke in Erlangen sowie Herrn Dr. Eggert im Schaltwerk Berlin für die anregenden Diskussionen.     

Study of the absorption spectra of the 4f electron transition of the Nd and Er complexes with 2-isobutylformyl-1,3-dione-indane in the presence of TX-100 and its analytical application

The absorption spectra of 4f electron transitions of the systems of neodymium and erbium with 2-isobutylformyl-1,3-dione-indane and TX-100 have been studied by normal and derivative spectrophotometry. Their molar absorptivities at the maximum absorption bands are about 7.2 (at 571 nm) times greater for neodymium and 13.1 (at 519 nm) times greater for erbium than those in the absence of the complexing agents. Use of second derivative spectra both eliminates the interference from other rare earths and increases the sensitivity from neodymium and erbium. Beers law is obeyed from 020 g/ml for neodymium and 025 g/ml for erbium. The relative standard deviations are 1.2% and 1.6% for 5.0 g/ml of neodymium and 8.0 g/ml of erbium, respectively. The detection limits (signal-to-noise ratio=2) are 0.14 g/ml and 0.20 g/ml. A method for the direct determination of neodymium and erbium in rare earth mixtures with good accuracy and selectivity is proposed.     

interferences in the measurement of arsenic by the method of vašák and šedivec

Summary In the measurement of arsenic by the method ofVaák andedivec, different wavelengths have been used to measure the concentration of the arsenic diethyldithiocarbamate. Such differences may be explained by the possible presence of silver nitrate in the silver salt solution. The absorbance should be measured at 522 nm when the salt is properly purified.The authors also measured the interference of antimony on the arsenic determination in the concentration range of 50–450g.

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Zusammenfassung Bei der Arsenbestimmung nachVaák undedivec wurden verschiedene Wellenlängen zur Messung der Konzentration des Arsendiäthyldithiocarbamats verwendet. Diese Unterschiede können mit der möglichen Anwesenheit von Silbernitrat in der Silbersalzlösung erklärt werden. Die Absorption sollte bei 522 nm gemessen werden, wenn das Salz gut gereinigt ist. Außerdem wurde die Störung durch Antimon (50 bis 450g) geprüft.

     

Nuclear interferences of uranium and thorium in a reactor neutron activation analysis determination of cerium using the radionuclides141Ce and143Ce

The interference contributions of uranium and thorium to the determination of cerium based on radionuclides¹⁴¹Ce and¹⁴³Ce produced by irradiation in a reactor core was determined. The values of the interference contributions for¹⁴¹Ce were 0.28±0.01 g Ce/g U and /2.01±0.05/x10^–3 g Ce/g Th, and for¹⁴³Ce 1.33±0.03 g Ce/g U and /9.0±0.2/x10^–3 g Ce/g Th.     

Zur Verteilung von Dotierungsstoffen in Selengleichrichterplatten

Zusammenfassung Zur schichtweisen Analyse von Spuren Chlor in Selengleichrichterplatten wird das Selen mit wäßriger Cyanidlösung in etwa 1 starken Schichten von diesen abgelöst. Für die quantitative Analyse des darin befindlichen Chlors eignet sich seine oxydativ-destillative Abtrennung als Chlorcyan mit Hilfe von Peroxidisulfat in schwefelsaurer Lösung. Als Absorptionsflüssigkeit dient ein Gemisch aus Äthanol, Pyridin und Barbitursäure, in der die letzten beiden Reagentien mit Chlorcyan unter Bildung eines Polymethinfarbstoffes reagieren, der direkt photometriert werden kann. Nach vorliegendem Verfahren lassen sich Spuren Chlor bis herab zu 2 g mit einer Varianz von ± 5% bestimmen. Das entspricht einer Grenzkonzentration von 0,02 g/ml. Mit Hilfe dieses Verfahrens kann die Chlorverteilung in der etwa 50 starken Selenschicht der Gleichrichterplatte ermittelt werden.

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On the distribution of doping elements in selenium rectifier cellsI. Method for the determination of the distribution of chlorine in selenium rectifier cells

The dissolution of the selenium in ca. 1 layers is realised by aqueous solutions of alkali cyanides. The quantitative analysis of chlorine in these solutions is possible by an oxydative destillation with persulphuric acid for the separation of chlorine as cyanogen chloride. During its absorption in a mixture of ethanol pyridine and barbituric acid it reacts to a highly coloured polymethine dye, which can be measured immediately. According to this method traces of chlorine up from 2 g can be determined with an accuracy of ± 5%, i.e. a limit of identification of 0.02 g/ml. Also the distribution of chlorine in the 50 selenium layer of the rectifier cell can be determined.

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Der Fa. Siemens AG danken wir für die Genehmigung zur Veröffentlichung der Ergebnisse, Herrn Dr. Iwantscheff und Herrn Ernst im Forschungszentrum der Siemens-Schuckert-Werke in Erlangen für anregende Diskussionen und Frau B. Jaetsch sowie Herrn Corinth für die Durchführung der Messungen.     

Mechanism of proton transfer from 2-nitrohexafluoropropane to amines

According to the analysis of NMR kinetic data, the proton transfer from the CH-acid 2-nitrohexafluoropropane to trioctylamine occurs in a hydrogen-bonded complex. The value of the k_H/k_D ratio (6) and the linearity of the ln k vs. T^–1 dependence indicate a classical mechanism of the process.

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2- . . , . k_H/k_D 6 .

     

Temperature effect on the composition and activity of iron(III) stearate based organometallic catalysts in hydrogenation reactions

The observed temperature dependence of the composition of FeSt₃–AlEt₃ catalytic system indicates that with increasing temperature the maximum catalytic activity and the content of the associated polynuclear complex change in parallel. This complex probably plays a decisive role in catalytic processes.

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FeSt₃–AlEt₃ . . , .

     

Simultaneous determination of copper,mercury and lead by first-order derivative spectrophotometry using dithizone as reagent

A first-order derivative spectrophotometric method has been developed for the simultaneous determination of copper, mercury and lead at g/L levels using dithizone as reagent. The procedure involves the simultaneous extraction of these elements by dithizone in chloroform from weakly alkaline solutions. Linear calibration curves were obtained in the ranges 0.5–10 (Cu), 1–10 (Hg) and 1–10 (Pb) g present in 40 ml of aqueous phase with detection limits of 5 g/L (Cu) and 20 g/L (Hg and Pb). The R.S.D.s for 100 g/L of copper, mercury and lead were 2.5, 2.6 and 3.1% respectively, for 5 determinations. The method is applicable for the determination of copper and lead in marine sediment samples with good precision and accuracy.     

Simultaneous determination of cobalt,nickel and iron by multi-wavelength spectrophotometry

A method for the simultaneous spectrophotometric determination of cobalt, nickel and iron based on the formation of their complexes with 1,5-bis(di-2-pyridylmethylene) thiocarbonohydrazide is proposed. The absorption curves of these complexes overlap severely in the scanning range 390–510 nm. The analyte concentrations are calculated by a least squares fit of the pure spectra to the mixture spectra, which therefore makes the simultaneous determination of these metallic ions possible without tedious pretreatment. The detection limits afforded by the proposed method range from 0.05 g/ml for Fe and Ni to 0.1 g/ml for Co. Root-mean-squared errors of prediction of 0.085 g/ml for Co, 0.048 g/ml for Ni and 0.1172 g/ml for Fe were obtained using the wavelength range 400–510 nm and 0.147 g/ml for Co, 0.107 g/ml for Ni and 0.127 g/ml for Fe using the wavelength range 420–434 nm. The effect of interferences is studied and the proposed method is applied to analysis for the above elements in synthetic samples and real samples, such as biological materials and alloys.     

Effect of Surfactants on the Immobilization of 4-(2-Pyridylazo)resorcinol on Silochroms

The effect of cationic surfactants (cetyltrimethylammonium bromide, cetylpyridinium bromide, and tetrabutylammonium perchlorate) and a nonionic surfactant (OP-7) on the conditions of the immobilization of 4-(2-pyridylazo)resorcinol (PAR) on three types of silica gel (Silochrom S-120 (200–350 m), Silochrom S-120 (315–500 m), and Silochrom S-80 (200–350 m)) was studied. It was found that OP-7 does not affect the adsorption of surfactants. The effect of cationic surfactants increases in the order tetrabutylammonium perchlorate < cetyltrimethylammonium bromide < cetylpyridinium bromide. The adsorption activity of silica gels increases in the order Silochrom S-120 (315–500 m) < Silochrom S-80 (200–350 m) < Silochrom S-120 (200–350 m). Cetylpyridinium bromide provides full immobilization of PAR on silica gel Silochrom S-120 (200–350 m) in the pH range 2–9.     

Redox Properties of Trinuclear Osmium Carbonylhydride Clusters with Unsaturated Ligands

Schemes of redox transformations were proposed for osmium carbonylhydride clusters: trinuclear (-H)Os₃(-CR = CHR')(CO)_{1 0} (R = R' = H, Ph; R = H, R' = Ph), (-H)₂Os₃(₃-L)(CO)₉ (L = C = CHPh, CHCPh), tetranuclear CpMnOs₃ (-CH = CHPh)(-H)(-CO)(CO)_{1 1}, and trinuclear Os₃(₃-C = CHPh)(CO)₉. Two-electron reduction of the trinuclear clusters results in elimination of the unsaturated ligand with preservation of the metal framework.     

Fällungsanalyse im Mikrogrammbereich: Eine neue Methode

Zusammenfassung Eine neue Methode zur Durchführung gravimetrischer Bestimmungen im Mikrogrammbereich wurde beschrieben; diese beruht im wesentlichen darauf, daß der Niederschlag nicht mehr zusammen mit dem Filter, sondern nach Überführen mit einem geeigneten Lösungsmittel in einem separaten Wägegefäß gewogen wird.Die dazu nötigen Geräte und deren Herstellung wurden beschrieben. Nach dieser Methode wurden folgende Bestimmungen mit zufriedenstellender Richtigkeit durchgeführt: 2,5–25g Al, 5–50g Cu und 5–50g Zn mit Oxin, 2,5–25g Fe(III) und 2,5–25g Ti(IV) mit N-Benzoyl-phenylhydroxylamin, 5–50g Ni und 5–50g Cu mit Salicylaldoxim, 2,5–50g Co(II) und 2,5–50g Fe(III) mit -Nitroso--naphthol sowie 5–50g Chlorid als Silberchlorid.

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Precipitation analysis in the microgram-scale: A new method

Summary A new method for gravimetric determinations in the microgram-scale is described. This method is based on the fact that the precipitate is not weighed together with the filter but is transferred to a separate weighingvessel using a suitable solvent. The necessary simple devices and their use are described. The following determinations were carried out with satisfying accuracy: 2,5–25g Al, 5–50g Cu and 5–50g Zn with Oxine, 2,5–25g Fe and 2,5–25g Ti withN-benzoylphenylhydroxylamine, 5–50g Ni and 5–50g Cu with salicylaldoxime, 2,52–50g Co and 2,5–50g Fe with -nitroso--naphthol and 5–50g chloride as silver chloride.