Eine chelatometrische Methode zur Ca- und Mg-Bestimmung in Ca- und Mg-Inosithexaphosphat

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Polyvinylpyrrolidone adsorption and structural studies on homoionic Li-, Na-, K-, and Cs-montmorillonite colloidal suspensions

Structural aspects of dilute homoionic Li-, Na-, K-, and Cs-montmorillonite (M-montmorillonite) particle suspension (1 g/L) under low-electrolyte-concentration (0.1 mM MCl) conditions were characterized by static (absorbance or turbidity) and dynamic (photon correlation spectroscopy) light-scattering methods as well as by the adsorption behaviors of nonionic polyvinylpyrrolidone (PVP) mol wt 5,000 g/mol (LMW PVP) and mol wt 400,000 g/mol (HMW PVP). Taking Li-montmorillonite as a reference for a single plate particle, a particle size increase and a surface accessibility decrease to polymer adsorptions were measured along the Li, Na, K, and Cs series. The results are related to the existence of montmorillonite quasicrystals or tactoids in diluted suspension, whose stability increases along the same cation series. Molecular weight effects on the PVP surface accessibility are discussed in terms of permeation properties of the different M-montmorillonite particles. Modeling the results calculates an average number of plates in montmorillonite quasi-crystals and the surface area distribution of ultramicropores <0.7 nm and pores >0.7 nm in M-montmorillonite particles. It can also be demonstrated by applying hydrodynamic and electrokinetic methods that the measured high absorbance or turbidity increase of PVP-loaded montmorillonite particles is not due to aggregation phenomena but to a PVP contribution in the light-scattering intensity.     

Ionen-chromatographische Analyse von Mg, Ca, Mn und Zn mit Anwendungsbeispielen zur Ca-/Mg-Bestimmung

Zusammenfassung Es werden die Trennmöglichkeiten für Ca, Mg, Sr, Mn, Zn, Ni und Pb an einem kommerziell erhältlichen Kationenaustauscher geringer Kapazität mit einem Gemisch aus Ethylendiamin und Citronensäure sowie anderen organischen Säuren als mobile Phasen ermittelt. Die Abhängigkeiten der Retentionszeiten von der Konzentration an Ethylendiamin und Citronensäure sowie vom pH-Wert werden untersucht. Die quantitativen Analysen erfolgen mittels eines Leitfähigkeits-Detektors. Für Ca und Mg ergeben sich Nachweisgrenzen von 20 bzw. 10 ppb (0,4 bzw. 0,2 ng in der Meßzelle). Anwendungsbeispiele für Wasser, Boden und Gestein mit Vergleichen zur komplexometrischen Titration werden vorgestellt.

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Ion-chromatographic analysis of Mg, Ca, Mn and Zn together with application examples for Ca/Mg determination

Summary The possibilities were found out for the separation of Ca, Mg, Sr, Mn, Zn, Ni and Pb on a commercial cation-exchanger column of low capacity by ethylendiamine and citric acid and other organic acids mixtures as eluents. The dependences of retention times on concentrations of ethylendiamine and citric acid as well as on the pH value were investigated. Quantitative analyses were carried out by means of a conductivity detector. For Ca and Mg the detection limits are 20 and 10 ppb resp. (0.4 and 0.2 ng resp. in the detector cell). Application examples for water, soil and rock with comparisons to the complexometric titrations are presented.

     

Complexes of Na-, Ca-, and Zn-montmorillonites with an aminated cyclodextrin

The uptake of mono-(6--aminoethylamino-6-deoxy)--cyclodextrin (CDen) by Na-, Ca- and Zn-montmorillonites has been examined at 25°C. Each of the first two minerals forms only one intercalated phase in which the CDen molecules are intercalated as a monolayer, while the third yields a mixture of two intercalated phases whose interlayer spaces are occupied by mono- and bilayers of the guest molecules. Intercalation proceeds by ion exchange with the interlayer cations for the Na-complex and by forming metalaminoethylamino chelate complexes for the others.Presented at the Fourth International Symposium on Inclusion Phenomena and the Third International Symposium on Cyclodextrins, Lancaster, U.K., 20–25 July 1986.     

Flammenphotometrische Calcium- und Strontiumbestimmung

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Complexation of Na-, Ca-, and Cu-montmorillonites with some parent and methylated cyclodextrins

The uptake of -, -, -, hexakis-2,6-di-O-methyl--(DM--), heptakis-2,6-di-O-methyl--(DM--) and heptakis-2,3,6-tri-O-methyl-- (TM--) cyclodextrins (CD's) by Na-, Ca-, and Cu-montmorillonites has been studied at 25°C. Each of -, DM--, DM--, and TM--CD's forms a complex with all of these montmorillonites in which the guest molecules are arranged as a monolayer with their open faces parallel to the silicate sheet of montmorillonite. On the other hand, -CD is intercalated only by the Na form and -CD cannot be taken up by any of the clays used. The interlayer spacing of the -CD complex varies from 18.0 to 21.5 Å with replacement of the interlayer cation, but those of the methylated -and -CD complexes remain unchanged, beingca. 21 and 18 Å, respectively. The different behaviour of the parent and methylated CD's is explained in terms of the structural and physicochemical characteristics of the individual CD's and interlayer cations.     

Flammenphotometrische Kalium- und Natriumbestimmung in Wein

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Physical properties of silicene electrodes for Li-, Na-, Mg-, and K-ion batteries

The transition from lithium-ion batteries to sodium- and potassium-ion batteries will increase the power of electrochemical current sources and the rate of their charging. On the basis of the first principles of density functional theory and ab initio molecular dynamics simulations, the interaction of Li, Na, Mg, and K atoms with an autonomous silicene has been studied. The adsorption energies and the Si–Me (Me?=?Li, Na, Mg, K) bond lengths for different locations of the adsorbed metal atoms are calculated. The favorable adsorption site of Me on silicene nanosheet is identified and reported. In the approximation of the generalized gradient, the band structure of the “silicene/Me” systems is calculated. The metallic state of an autonomous metallized silicene can arise for various cases of adsorption of an alkali metal and when the ratio between the Mg and Si atoms in the system is 1:1. Metallization of the semiconductor does not occur when the number of adsorbed Mg atoms is less than the number of Si atoms.     

Flammenphotometrische Natrium- und Kaliumbestimmung im Serum

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Flammenphotometrische Bestimmung von Natrium in Uran, Phosphat, Carbonat und Silicatgesteinen

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Flammenphotometrische Bestimmung von Spurenmengen Lithium, Natrium, Kalium und Calcium

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Flammenphotometrische Bestimmung von Natrium und Kalium in Manganerzen

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Flammenphotometrische Bestimmung von Caesium und Rubidium in Whisky

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Flammenphotometrische Bestimmung kleiner Calciumgehalte in Zirkonium und dessen Legierungen

Zusammenfassung Zur Abtrennung kleiner Gehalte an Calcium aus Zirkonium und dessen Legierungen wird die Metallprobe im Chlorstrom aufgeschlossen; das dabei gebildete ZrCl₄ sowie flüchtige Chloride von Legierungspartnern werden dann im Wasserstrahlvakuum absublimiert. Die radiochemische Überprüfung der Abtrennungsoperation ergab, daß im Mittel 92% des vorliegenden Calciums im Destillationsrückstand verbleiben und dort nach Lösen in Salpetersäure-Flußsäure und Verdünnen mit Aceton blammenphotometrisch bestimmt werden können. Bei einer Einwaage von 1 g liegt die Nachweisgrenze bei 2 ppm Ca; die Reproduzierbarkeit der Bestimmungen im 20 ppm-Bereich beträgt ±10%.

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Summary Trace amounts of Ca are separated from the matrix by treating the sample with a stream of chlorine and subliming the ZrCl₄ formed and other volatile chlorides of alloying components in vacuo. A radiochemical investigation of the separation revealed, that 92% of the Ca present remain in the residue of the sublimation. After dissolution of the residue in nitric acid-hydrofluoric acid and dilution of the sample with acetone, Ca is determined by flame photometry. The limit of detection is 2 ppm with a sample size of 1 g, the reproducibility at the 20 ppm level is ±10%.

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Frl. R. Franke möchte ich für die wertvolle Mitarbeit bei der Ausarbeitung des Verfahrens und bei der Durchführung zahlreicher Analysen danken, Herrn Dr. W. Gebauhr für sein förderndes Interesse an der vorliegenden Arbeit.     

High H2 uptake in Li-, Na-, K-metalated covalent organic frameworks and metal organic frameworks at 298 K

The Yaghi laboratory has developed porous covalent organic frameworks (COFs), COF102, COF103, and COF202, and metal-organic frameworks (MOFs), MOF177, MOF180, MOF200, MOF205, and MOF210, with ultrahigh porosity and outstanding H(2) storage properties at 77 K. Using grand canonical Monte Carlo (GCMC) simulations with our recently developed first principles based force field (FF) from accurate quantum mechanics (QM), we calculated the molecular hydrogen (H(2)) uptake at 298 K for these systems, including the uptake for Li-, Na-, and K-metalated systems. We report the total, delivery and excess amount in gravimetric and volumetric units for all these compounds. For the gravimetric delivery amount from 1 to 100 bar, we find that eleven of these compounds reach the 2010 DOE target of 4.5 wt % at 298 K. The best of these compounds are MOF200-Li (6.34) and MOF200-Na (5.94), both reaching the 2015 DOE target of 5.5 wt % at 298 K. Among the undoped systems, we find that MOF200 gives a delivery amount as high as 3.24 wt % while MOF210 gives 2.90 wt % both from 1 to 100 bar and 298 K. However, none of these compounds reach the volumetric 2010 DOE target of 28 g H(2)/L. The best volumetric performance is for COF102-Na (24.9), COF102-Li (23.8), COF103-Na (22.8), and COF103-Li (21.7), all using delivery g H(2)/L units for 1-100 bar. These are the highest volumetric molecular hydrogen uptakes for a porous material under these thermodynamic conditions. Thus, one can obtain outstanding H(2) uptakes with Li, Na, and K doping of simple frameworks constructed from simple, cheap organic linkers. We present suggestions for strategies for synthesis of alkali metal-doped MOFs or COFs.     

Flammenphotometrische Bestimmung von Kalium und Natrium in Heu und anderen pflanzlichen Substanzen

Ohne ZusammenfassungDiese Eichkurven können auch für andere pflanzliche Substanzen angewandt werden. Bei der Untersuchung anderer biologischer Substanzen müssen entsprechende Eichkurven aufgenommen werden.     

Zur schnellen, empfindlichen und genauen Bestimmung des Na- und K-Gehaltes in biologischen Materialien

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Die gegenseitige Schutzwirkung der kolloiden Mg-, Ca-, Sr- und Ba-Karbonate

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