Use of non-segmented flow,post-columns reaction detection with miniaturized HPLC systems

Summary The use of non-segmented flow, post-column reaction detection is evaluated for use with miniaturized HPLC. Non-segmented open-tubular reactors with internal diameters 0.1 mm to 0.25 mm and packed-bed reactors with internal diameters of 1 mm, filled with 5 and 10 m particles are evaluated theoretically and experimentally with respect to band broadening and pressure drop characteristics. An integrated system consisting of miniaturized HPLC (1 mm i. d.) columns and compatible hardware is described. An example of the separation of catecholamines is given.     

Semiquantitative determination of thiourea,thiocyanate, and sulfide by circular thin layer chromatography

Summary A method for semiquantitative determination of thiourea, thiocyanate, and sulfide is described. It involves making circular spots or rings on chromatoplates using the circular thin layer Chromatographic apparatus. The method is based on sensitivity and specificity of spot reactions and comparison of the color intensity of a circular spot with that of sensitivity standards. The accuracy of the method is ± 5% and the procedure is rapid, simple and economical.

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Zusammenfassung Ein Verfahren zur halbquantitativen Bestimmung von Thioharnstoff, Thiocyanat und Sulfid wurde beschrieben. Es beruht auf der chromatographischen Herstellung kreisförmiger Flecken oder Ringe auf Dünnschichtplatten. Mit empfindlichen und spezifischen Tüpfelreaktionen wurden die Flecken gefärbt und die Farbintensität mit Standardproben verglichen. Die Genauigkeit beträgt ± 5%.

     

Zur komplexchemie von 4-zentren-π-systemen : VIII. ESR-untersuchungen an heterobutadien-chelaten. I. Kalium-(diazabutadien-tetracarbonyl-metallate)

Glyoxal- and diacetyl-bis(imine)metal tetracarbonyls (RNCR′CR′NR)M(CO)₄ (M = Cr, Mo, W) are reduced with potassium in DME to give paramagnetic mono-anions. Their high-resolutior, ESR spectra show the hyperfine splittings of the magnetically active ligand atoms as well as the satellites of the metal isotopes ⁵³Cr,^95,97Mo and ¹⁸³W. The coupling constants are discussed with respect to π-bonding mechanisms.     

Secondary-ion mass spectrometry of some catalpol and mussaenoside derivatives

The iridoid glycosides catalpol, veronicoside, catalposide, mussaenoside, and 8-epiloganin have been investigated by secondary-ion mass spectrometry (SIMS). A tendency of these compounds to give cationized1 form of the molecular ions in the SIMS regime has been shown. In the SIMS spectra of veronicoside and catalposide the maximum peaks were those of acyl cations, and in the cases of mussaenoside and 8-epilonganin they were the peaks of ions formed by the elimination of a glucose molecule.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 89 14 75. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 62–65, January–February, 1996. Original article submitted Spetemebr 17, 1995.     

Fluorescence quenching of alternant and non-alternant polycyclic hydrocarbons by electron transfer

Rate constants of fluorescence quenching by electron acceptors are greater for alternant than for non-alternant hydrocarbons with equal E_oo. The reverse is true for quenching by electron donors. This is consistent with the lowering of the π-orbital energies of non-alternant compared to alternant polycyclic hydrocarbons of equal E_oo.     

Bis(dialkylmetal)-N,N′-dimethyloxamides of aluminium,gallium and indium,preparation, physical and spectroscopic properties

The reaction of N,N′-dimethyloxamide with trialkyl derivatives of aluminium, gallium, and indium yields bis(dialkylmetal) compounds of structural formula (R₂M)₂[O₂C₂(NCH₃)₂] (M = Al, Ga, In; and R = CH₃, C₂H₅). The M₂O₂C₂N₂ skeleton of these monomeric products forms an almost planar system of two fused five-membered rings, with S₂ symmetry. For the dimethylgallium and dimethylindium derivatives, ¹H and ¹³C NMR spectra show the presence of two conformational isomers which differ in the orientation of the N-methyl relative to the two metal-bound CH₃ groups.     

Precise atomic masses of147Eu,147Gd,and151Tb derived from their decay properties

Theβ-decay energies of¹⁴⁷Eu,¹⁴⁷Gd, and¹⁵¹Tb were determined by usingγ-spectroscopical methods. The comparison of experimental with calculatedK-capture probabilities yielded theQ _EC values 1.690( _?16 ⁺²¹ )MeV and 2.203( _?13 ⁺¹⁹ )MeV for¹⁴⁷Eu and¹⁴⁷Gd, respectively. By measuring the ratio of positron decay to electron capture for two branches in¹⁴⁷Eu decay, the decay energiesQ _EC=1.702(13) MeV andQ _EC=1.709(18)MeV were derived. Also fromEC/β ⁺ ratios the valuesQ _EC=2.225(75) MeV for¹⁴⁷Gd, andQ _EC=2.566(12)MeV for¹⁵¹Tb were obtained. Earlier discrepancies in the mass adjustment of these isotopes were removed. In course of the present studiesγ-decay properties of¹⁴⁷Eu and¹⁴⁷Gd were reinvestigated.     

Use of γ-γ Coincidence Spectrometry in the Geochemical Study of Diamictites from South Africa

We used - coincidence spectrometry to investigate the possible presence of a meteoritical component in 27 samples of South African diamictites. Recently, several studies have suggested that some tillites/diamictites may represent impact breccias, but a petrographical study by our group found no evidence for the presence of impact-characteristic shocked minerals. The siderophile elements, such as Cr, Co, Ni, and, especially, the platinum group elements, have high abundances in meteorites, but low abundances in terrestrial crustal rocks. The Ir content of the diamictites was measured with the new iridium coincidence spectrometer (ICS) at the University of Vienna, with detection limits of around 0.02 ppb. No enrichments in the contents of Ir and other siderophile elements compared to average crustal concentrations were found; thus, no unequivocal evidence for an impact origin of these diamictites of the South African Dwyka Group can be documented.     

Über Verbindungen der Siliciumtetrahalogenide mit aromatischen N-Heterocyclen: Bestätigung und Berichtigung

Zusammenfassung Von den früher⁶ beschriebenen Additionsverbindungen zwischen Siliciumtetrahalogeniden und Pyridin bzw. seinen Homologen konnten J₄Sipy ₄ ⁷ und HSiCl₃ py ₂ eindeutig bestätigt und in ihren Eigenschaften wie einigen chemischen Reaktionen näher festgelegt werden. Nicht dagegen existieren Verbindungen zwischen SiJ₄ und Chinolin, -Picolin, Acridin oder Collidin. SiF₄ bildet bei direktem Einleiten in Chinolin eine bereits kurz oberhalb Raumtemperatur zersetzliche Additionsverbindung F₄Si(chin)₂.

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From addition compounds of silicon tetrahalogenides and pyridine, published⁶ in 1954, the somewhat doubtful J₄Sipy ₄ ⁷ and HSiCl₃ py ₂ could be confirmed and fixed in their properties as well as in some chemical reactions. On the contrary compounds between SiJ₄ and quinoline, -picoline, acridine and collidine do not exist. On passing SiF₄ directly into quinoline, an addition compound F₄Si(chin)₂ is formed which decomposes already at temperatures somewhat higher than room temperature.

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64. Mitt.:H. Bürger, M. Schulze undU. Wannagat, Inorg. Nucl. Chem. Letters3, 43 (1967).

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Zugleich 4. Mitt. über Verbindungen von Nichtmetallhalogeniden mit Pyridin und seinen Homologen; 3. Mitt.:U. Wannagat undG. Schindler, Angew. Chem.69, 784 (1957).

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Mit Auszügen aus der DissertationK. Hensen, Techn. Hochschule Aachen 1962.

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Mit Auszügen aus der DiplomarbeitP. Petesch, T. H. Aachen 1958.     

Alkylamino- und Dialkylamino-phenoxy-methylsilane

Zusammenfassung Alkyl-und Dialkylamino-phenoxy-methylsilane ließen sich sowohl durch Umsetzung von Phenoxy-methyl-chlorsilanen mit primären und sekundären Aminen unter Cl/NRR-Austausch als auch durch Reaktion von Phenoxymethylsilanen mit substituierten Alkaliamiden unter C₆H₅O/NRR-Austausch gemäß den Gl. (1) bis (6) darstellen. Ihre Eigenschaften sind aus Tab. 1 zu ersehen.

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We succeeded in preparing alkyl- and dialkylamino-phenoxymethylsilanes by reaction of phenoxy-methyl-chlorosilanes with primary and secondary amines (Cl/NRR-exchange) as well as by reaction of phenoxymethylsilanes with substituted alkaliamides (C₆H₅O/NRR-exchange)according equations (1) to (6). Their properties are to be seen in table 1.

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53. Mitt.:U. Wannagat undG. Schreiner, Mh. Chem.96, 1902 (1965).

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Mit Auszügen aus der DissertationG. Schreiner und der DiplomarbeitJ. Pohl, Techn. Hochsch. Graz, 1964.