Determination of heavy metals (Pb, Cd, Cu, Zn, Cr) in sedimentary reference materials with IDMS: total concentration and aqua regia soluble portion

Summary The total concentration and the aqua regia soluble portion of traces of Pb, Cd, Cu, Zn, and Cr are determined with isotope dilution mass spectrometry (IDMS) in three different types of sediments using a thermal quadrupole instrument (THQ). The results are compared with those obtained by other methods during a certification project to establish these sediments (BCR 277, BCR 280, BCR 320) as standard reference materials. The IDMS (THQ) results are in good agreement with the preliminary certification values and the results of two other laboratories, which applied IDMS using magnetic sector field mass spectrometers. Significant differences between the different analytical methods were found for the total Pb concentration, which could be explained by adsorption and coprecipitation effects during the chemical pretreatment of samples. Using aqua regia instead of HF/HNO₃ for the decomposition of sediments, only 65%–95% of the total Pb and 60%–90% of the total Cr could be dissolved. On the other hand, only a small or negligible portion of Zn, Cd, and Cu could not be dissolved by aqua regia. The IDMS values for the aqua regia soluble Cr portion are significantly higher compared to the results of other methods. This can be explained by adsorption effects.

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Bestimmung von Schwermetallen (Pb, Cd, Cu, Zn, Cr) in sedimentären Standard-Referenzmaterialien mit massenspektrometrischer Isotopenverdünnungsanalyse: Totalgehalt sowie in Königswasser löslicher Anteil

     

Industrielle Systemforschung

Zusammenfassung Der Begriff "Automatismus" wird begründet und der Beitrag der Informationstheorie und Kybernetik zur Verwirklichung des industriellen Automatismus diskutiert.

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Summary The concept of "automatism" is established and the contribution of information theory and cybernetics towards the realization of industrial automatism is discussed.

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Résumé Le concept d' "automatisme" est établí et la contribution de la théorie de l'information et la cybernetique à la réalization de l'automatisme industriel est discuté.

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Berichtet am Internationalen Kongreß für Automatik: Madrid, 13.–18. Oktober 1958. Siehe auch [1].     

Tris-[2.21]- and tris-[2.2.2]-σ-homobenzenes

Tris-[2.2.1]- and tris-[2.2.2]-σ-homobenzenes are synthesised by reaction of 1,1′-bicyclobutenyl with appropriate dienophiles and hydrogenation of the adducts.     

Über einige Umsetzungen von 2,5-Diamino- sowie 2-Amino-1,3,4-thiadiazolen mit α-Halogenketonen zu Imidazo[2,1-b]-1,3,4-thiadiazolen

2,5-Diamino-1,3,4-thiadiazole (1) reacts with -halogencarbonyl compounds to 2-imino-3-phenacyl(acetonyl)-5-amino-1,3,4-thiadiazolines (3) which easily can be cyclised to 2-amino-6-aryl (alkyl)-imidazo[2,1-b]-1,3,4-thiadiazoles (4), the structure of which was proofed.On the basis of the amino function in position 2 these substances were able to form easilySchiff bases (5, 6, 7). Their semicyclic amidine system did not allow as yet to integraet it in a third ring system.

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8. Mitt. über Heterocyclen; 7. Mitt.:A. Sitte, R. Wessel undH. Paul, Mh. Chem.106, 1291 (1975).     

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Half a Century of Polystyrene—A Survey of the Chemistry and Physics of a Pioneering Material

Hermann Staudinger, the founder of polymer chemistry, would have been 100 years old this year. One of the key materials with which he elucidated the structure of high polymers was polystyrene.—Polystyrene, one of the most important thermoplastics, has now been manufactured industrially for some 50 years. Not only has it simplified our daily lives in a variety of ways, it has also been a model substance for the development and expansion of polymer chemistry and polymer physics, and it was the pioneering material for handling polymer solutions and melts. This article surveys the development and present state of knowledge of the polymerization of styrene and of the relationships between structure and properties.