Glass capillary gas chromatography of amino acid enantiomers

Glass capillaries coated with Chirasil-Val, a chirally functionalised polysiloxane, are capable in principle of resolving all protein amino-acid enantiomers in a single run and within a short analysis time, thus allowing for example the quantitative amino acid determination by enantiomer labelling. The elution characteristics of the individual amino acids however are also dependent upon the chemical nature of the capillary wall surface, and a surface pretreatment is found to be necessary if all protein amino acids are to be analysed. Of the various methods of pretreatment tested, etching of borosilicate glass with gaseous HCl followed by deposition of colloidal silicic acid is considered to be the most suitable.     

Structure and reactivity of xanthocorrinoids. Part V. Formation of trans-diol derivatives of 5,6-dihydrocobyrinic acid from xanthocorrinoids under acidic conditions

On treatment with H₂SO₄/MeOH, epimerization of hexamethyl cis-5,6-dihydroxycobyrinate c,8-lactam ( 3 ) takes place quantitatively at C(6), yielding the corresponding trans-diol 4 . The corresponding lactone 7 , whose structure has been established by X-ray analysis, is obtained from xanthocorrinoids 5 and 6 under similar conditions.     

Single- and multi-channel detection for generalized quantitative analysis in cases of unresolved chromatographic peaks

Computerized quantification of components under overlapping chromatographic peaks is done by calibration of chromatograms against component mixtures. For conventional (single-channel) detectors, the limitations of earlier methods based on ordinary multiple regression, can be circumvented by data reduction with the aid of principal component analysis with the partial least-squares approach. Simulation studies show that the method can be applied even when there is severe peak overlap, unstable baseline, noisy chromatograms or non-linear detector response. Advantages in the quantification of fused peaks by means of multichannel detectors are outlined. Present limitations on the quantitative evaluation of several overlapping component peaks from a single spectro-chromatogram by means of the partial least-squares method combined with multiple regression on the pure component spectra, are discussed with respect to practical high-performance liquid chromatography.     

An Alternative to Automatic Titration

Automatic titrators are designed to do exactly what a lab-technician used to do. Much more sophisticated automation of volumetry is possible. Omegaphoresis [3] in buffer-free [2] sample solutions automatically creates a stationary multiple component titration curve or zoned pattern with normalized concentrations of each separated species. An automatic measurement of each zone length yields their quantity. Simultaneous automatic detection of all the zones in a 10–20 component solution in less than 2 minutes, with a precision of ±2%, a required amount of the order of less than one nanomol and a resolution of ±pK < 0.01 replaces acid-base, complexometric, and certain types of redox-titrimetry. An option of the method allows identification of the components as well.     

Metabolism of Carotenoids in Salmonids. Part 3. Metabolites of astaxanthin and canthaxanthin in the skin of atlantic salmon (salmo salar,L.)

Diets supplemented with astaxanthin and canthaxanthin, respectively, and a control diet without carotenoid additions, were fed to 1½-year-old Atlantic salmon (Salmo salar, L.) for one year. The integuments were investigated as to their quantitative and qualitative carotenoid composition. Astaxanthin and canthaxanthin deposited in the skin amounted to 20 and 14% of the total carotenoids only. Seventy % must be considered as metabolites of astaxanthin and canthaxanthin and 10% as basic xanthophylls also present in the control groups. Astaxanthin apparently underwent the following metabolic pathway: astaxanthin→idoxanthin→adonixanthin→zeaxanthin→zeaxanthin 5,6-epoxides. Reduction of the 4′-carbonyl group was stereospecific leading to the (4′R)-idoxanthin. Canthaxanthin was obviously converted to β,β-carotene via 4′-hydroxyechinenone, echinenone, and 4-hydroxy-β,β-carotene.     

Analyse heterogener Legierungen durch Isolierung und durch Lokalanalyse mit der Elektronenstrahl-Mikrosonde

Zusammenfassung Die beiden wichtigsten Verfahren zur quantitativen Analyse der Gefügebestandteile heterogener Legierungen sind die potentiostatische Isolierung und die Lokalanalyse mit der Elektronenstrahlmikrosonde. Manganstähle mit Carbiden definierter Zusammensetzung und Größe boten die Möglichkeit, erstmalig die quantitativen Aussagen dieser beiden Methoden miteinander zu vergleichen.Dabei erbrachte die Isolierung durch die gleichzeitige analytische Erfassung größerer Mengen der Matrix und der Carbidphasen sehr genaue Angaben ihrer durchschnittlichen Zusammensetzung. Örtliche Konzentrationsänderungen in derselben Phase werden jedoch nicht erfaßt. Dagegen zeigte sich, daß die lokale Röntgenspektralanalyse zwar vergleichbare Ergebnisse lieferte, aber auch bei Anregung mit einem feinfokussierten Elektronenstrahl (Durchmesser <1) die Genauigkeit der Werte bei Teilchengrößen <5 durch Anregung von Nachbarbereichen merkbar beeinflußt wird.Zerlegung und Phasenanalyse einerseits sowie Lokalanalyse mit der Elektronenstrahlmikrosonde anderseits haben ihren eigenständigen Anwendungsbereich. Unter Berücksichtigung der gegebenen Grenzen können sich beide Methoden zur Analyse metallischer Werkstoffe sinnvoll ergänzen.

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Summary The two most important procedures for the quantitative analysis of the structural constituents of heterogeneous alloys are the potentiostatic isolation and the local analysis by means of the electron beam microsonde. Manganese steels with carbides of definite composition and magnitude offered the possibility for securing quantitative statements for the first time with respect to the comparative merits of these two methods.The isolation gave very precise information concerning the average composition through the concurrent analytical involvement of larger amounts of the matrix and the carbide phases. However, local alterations in the concentration within the same phase were not revealed. On the other hand, it was found that though the local X-ray spectral analysis yielded comparable results, the accuracy of the values at particle sizes <5 is markedly influenced through excitation of neighboring regions when the excitation was due to a fine-focused electron beam (Ø <1).Decomposition and phase analysis on one hand and local analysis with the electron beam-microsonde on the other have their individual fields of application. If the given limitations are taken into account, both methods may contribute judiciously to the analysis of metallic industrial materials.

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Résumé L'isolement potentiostatique et l'analyse locale par la microsonde électronique représentent les deux procédés les plus importants pour l'analyse quantitative des constituants entrant dans la texture des alliages hétérogènes. Les aciers au manganèse avec carbures en composition et quantité définies offrent la possibilité, pour la première fois, de comparer entre elles les indications quantitatives de ces deux méthodes.L'isolement par détermination analytique simultanée de plus grandes quantités de matrice et de la phase carbure a rendu des données très précises de leur composition moyenne. Les modifications de concentration locale dans la même phase n'ont pourtant pas été atteintes. Par contre, il s'est avéré que l'analyse spectrale locale par rayons X conduisait à des résultats comparables, mais en excitant par un faisceau d'électrons finement focalisé (Ø<1), l'exactitude de la valeur pour les particules de dimensions inférieures à 5 se trouve influencée de façon notable par excitation des régions voisines.La séparation et l'analyse des phases d'une part, l'analyse locale par la microsonde à faisceau d'électrons d'autre part, ont leur domaine d'application propre. En tenant compte des limites données, les deux méthodes peuvent se compléter d'une manière judicieuse pour l'analyse des produits métalliques oeuvrés.

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Vortrag anläßlich des Kolloquiums für metallkundliche Analyse mit besonderer Berücksichtigung der Elektronenstrahl-Mikroanalyse, Wien, 22. Oktober 1964.     

Indirect detection of magnetic resonance by heteronuclear two-dimensional spectroscopy

A new technique is proposed to indirectly record with high sensitivity the nuclear magnetic resonance of nuclei with a low gyromagnetic ratio. The method relies on a coherent transfer of transverse magnetization to nuclei of high gyromagnetic ratio.