Determination of metal ions by liquid chromatographic separation of their 2-acetylpyridine-4-ethyl-3-thiosemicarbazone chelates

A new thiosemicarbazone was prepared, characterized, and used as a complexing reagent for the chromatographic separation and determination of metal complexes by reverse-phase HPLC. The reagent was sufficiently soluble in methanol-water solutions for metal ions to be complexed in this aqueous organic phase, without need for extraction. Many variables affected the retention times of the metal complexes. Several metals were determined selectively by complexation with the reagent and chromatographic separation of the complexes. Interference effects from other metal ions were also investigated.     

High resolution mass spectrometric studies of some bicyclic γ-lactones

The mass spectra of three bicyclic γ-lactones have been studied, and the fragmentation pathways have been proposed with the aid of accurate mass measurements and metastable transitions. An unusually low [M ? CH₃] ion and the presence of an abundant [M ? C₅H₉] ion in the mass spectrum of dihydroactinidiolide were interpreted as a possible rearrangement involving a methyl migration. The eliminations of methyl radical, carbon monoxide and ketene are important processes in many cases.     

Zur Synthese von Derivaten des Pyrido[1,2-a]azepins

On the Synthesis of Derivatives of Pyrido[1,2-a]lazepine The conjugated pyridinium ylides of type 4 undergo 8π -electrocyclisation affording the heterobicyclic allenes 5 which, in the presence of H₂O and H₂O₂, are subsequently transformed into the substituted pyrido[1,2-a]-azepinones 6, a novel heterocyclic system. The chemical behaviour of 6a,b is dominated by cleavage of the lactam bond and subsequent reaction to pyridinc and isoquinoline derivatives, respectively; e.g. reaction of 6a, b with 4,5-dihydro-4-methyl-3H-1,2,4-triazole-3,5-dione affords the cycloadducts 11 and 12 almost quantitatively. The successful transformation of 6b into 15 is described, the latter being the first representative of the presently unknown, potentially antiaromatic pyrido[1,2-a]azepine ( 1 ).     

Papierchromatographische Trennungen von Alkaloidgemischen an Succinylzellulose-Papieren

Zusammenfassung Das früher beschriebene¹ Succinylzellulose-Papier wird als Ionenaustauscher zur weiteren papierchromatischen Trennung von Basengemischen verwendet. Getrennt wurden die Alkaloide der Morphingruppe und deren Abwandlungsprodukte, ferner die Alkaloide der Strychnin-, der Tropin-, der Cocaingruppe und andere Alkaloide.

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Summary The succinyl-cellulose paper described previously¹ is used as ion exchanger for additional paper chromatographic separations of mixtures of bases. Separations were accomplished of the alkaloids of the morphine group and their modification products, and also of the alkaloids of the strychnine-, tropine- and cocaine groups and other alkaloids.

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Résumé On utilise le papier à la succinyl-cellulose déjà décrit¹, comme écharigeur d'ions pour d'autres séparations par chromatographie sur papier de mélanges basiques. On a séparé ainsi les alcaloïdes du groupe de la morphine et leurs produits d'évolution, et en outre, les alcaloïdes des groupes de la strychnine, de la tropine et de la cocaïne et d'autres alcaloïdes.

     

Numerical stability of biorthogonal wavelet transforms

For orthogonal wavelets, the discrete wavelet and wave packet transforms and their inverses are orthogonal operators with perfect numerical stability. For biorthogonal wavelets, numerical instabilities can occur. We derive bounds for the 2-norm and average 2-norm of these transforms, including efficient numerical estimates if the numberL of decomposition levels is small, as well as growth estimates forL . These estimates allow easy determination of numerical stability directly from the wavelet coefficients. Examples show that many biorthogonal wavelets are in fact numerically well behaved.