Multi-residue off-flavour profiling in wine using stir bar sorptive extraction–thermal desorption–gas chromatography–mass spectrometry

A multi-residue method (MRM) for the detection and quantification of eight compounds responsible for off-flavours in wine using stir bar sorptive extraction (SBSE) followed by thermal desorption (TD) and gas chromatography–mass spectrometry (GC–MS) analysis is presented. The extraction and desorption conditions were optimised in order to get the best compromise for the simultaneous analysis of the eight target solutes, belonging to different chemical classes. The analytical conditions enable the quantification of the solutes below their respective organoleptic perception thresholds in wine. The method displayed good linearity over the concentration ranges explored in wine as well as excellent repeatability (RSD below 6%) and good reproducibility (RSD below 24%). The developed methodology was applied to the analysis of several wines and showed good agreement with the results collected with headspace solid-phase microextraction (HS-SPME) or liquid–liquid extraction (LLE) followed by GC–MS or electron capture detection (ECD). Good correlation was also found between the analytical and sensory results.     

Synthesis and Reactivity of an Early‐Transition‐Metal Alkynyl Cubane Mn4C4 Cluster

While the coordination chemistry of monometallic complexes and the surface properties of extended metal particles are well understood, the control of metal nanocluster formation has remained challenging. The isolation of discrete metal clusters provides an especially rare snapshot at the nanoscale of cluster growth. The synthesis and full characterization of the first early‐transition‐metal alkynyl cubane and the first μ³‐alkynyl Mn₃ motif are reported.     

How Does a Coordinated Radical Ligand Affect the Spin Crossover Properties in an Octahedral Iron(II) Complex?

The influence of a coordinated π‐radical on the spin crossover properties of an octahedral iron(II) complex was investigated by preparing and isolating the iron(II) complex containing the tetradentate N,N′‐dimethyl‐2,11‐diaza[3.3](2,6)pyridinophane and the radical anion of N,N′‐diphenyl‐acenaphtene‐1,2‐diimine as ligands. This spin crossover complex was obtained by a reduction of the corresponding low‐spin iron(II) complex with the neutral diimine ligand, demonstrating that the reduction of the strong π‐acceptor ligand is accompanied by a decrease in the ligand field strength. Characterization of the iron(II) radical complex by structural, magnetochemical, and spectroscopic methods revealed that spin crossover equilibrium occurs above 240 K between an S=1/2 ground state and an S=3/2 excited spin state. The possible origins of the fast spin interconversion observed for this complex are discussed.     

An interpolation theorem for proper holomorphic embeddings

Given a Stein manifold x of dimension n > 1, a discrete sequence , and a discrete sequence where , there exists a proper holomorphic embedding satisfying f(a _j ) = b _j for every j = 1,2,... Forstnerič and Prezelj supported by grants P1-0291 and J1-6173, Republic of Slovenia. Kutzschebauch supported by Schweizerische National fonds grant 200021-107477/1. Ivarsson supported by The Wenner-Gren Foundations.     

Fully Delocalized Mixed-Valent Cu1.5Cu1.5 Complex: Strong Cu-Cu interaction and Fast Electron Self-Exchange Rate Despite Large Structural Changes**

A flexible macrocyclic ligand with two tridentate {CNC} compartments can host two Cu ions in reversibly interconvertible states, Cu^ICu^I ( 1 ) and mixed-valent Cu^1.5Cu^1.5 ( 2 ). They were characterized by XRD and multiple spectroscopic methods, including EPR, UV/Vis absorption and MCD, in combination with TD-DFT and CASSCF calculations. 2 features a short Cu⋅⋅⋅Cu distance (≈2.5 Å; compared to ≈4.0 Å in 1 ) and a very high delocalization energy of 13 000 cm⁻¹, comparable to the mixed-valent state of the biological Cu_A site. Electron self-exchange between 1 and 2 is rapid despite large structural reorganization, and is proposed to proceed via a sequential mechanism involving an active conformer of 1 , viz. 1′ ; the latter has been characterized by XRD. Such electron transfer (ET) process is reminiscent of the conformationally gated ET proposed for biological systems. This redox couple is a unique pair of flexible dicopper complexes, achieving fast electron self-exchange closely related to the function of the Cu_A site.     

Cu0-catalysed 1,3-dipolar cycloadditions of α-amino acid derived N,N-cyclic azomethine imines to ynones

A series of 20 CuAIAC reactions between eight 4-acylamino substituted pyrazolidine-3-one-1-azomethine imines and four terminal ynones were performed using Cu⁰ as catalyst. The corresponding fluorescent cycloadducts were obtained in very high yields upon simple workup. Thus, Cu-metal turned out to be a better catalyst than Cu^I in terms of yield and ease of isolation. Availability of azomethine imines, mild reaction conditions, and simple workup enable a “click” access to libraries of densely substituted 2,3-dihydro-1H,5H-pyrazolo[1,2-a]pyrazol-1-ones. Reactivity of differently substituted dipoles was evaluated experimentally and by quantum chemical methods (DFT).     

Spin Physics and the Theory of Strong Interactions

Taking the Minkowski space as the scene of quantum field theory implies an implicit assumption: the spin plays no dynamical role. This assumption (already challenged by reggeism) should be re-examined in the light of recent advances of experimental spin physics. To make a dynamical role of spin possible, it is proposed to use as a scene for the theory of strong interactions the whole Poincaré group. On the other hand characteristic functions, defined on the Poincare group, provide the only known way to describe the distinctive peculiarity of resonances, namely that a resonance is both one particle and several particles. Regge trajectories are interpreted as evidence for a mass-spin correlation among the virtual hadrons of vacuum. It is conjectured that the form of this correlation is deducible from a central limit theorem on the Poincare group. And that a statistical mechanics of hadronic vacuum is important for strong interaction theory.     

Identifizierung organischer Substanzen mit Hilfe der Gaschromatographie. Eine neue Variante chromatographischer Spektren

Zusammenfassung Eine Methode zur Identifizierung der Kohlenwasserstoffe an Hand sogenannter chromatographischer Spektren wird beschrieben. Im Gegensatz zu der älteren Methode, wobei sich die zu identifizierende Verbindung in vier verschiedene, parallel geschaltete Kolonnen mit unterschiedlichen stationären Phasen verteilt und nach ihrem Durchgang wieder in einem Detektor vereinigt wird, wird bei dieser neuen Variante so vorgegangen, daß die organische Verbindung zuerst durch eine Kolonne und nachher durch zwei parallel angeordnete Kolonnen läuft. Man erhält ein Chromatogramm, an dem man sehr leicht ablesen kann, zu welchem Kohlenwasserstofftyp eine Komponente gehört, bzw. man kann das Chromatogramm mit dem einer Standardsubstanz vergleichen und so die Identität feststellen.

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Summary A method is described for identifying hydrocarbons by means of so-called Chromatographic spectra. In contrast to the older method, in which the compound to be identified is divided into four different parallel connected columns with differing stationary phases and then reunited in a detector after their passage, the procedure in this new variant is pass the organic compound through a column first and then through two parallel columns. A chromatogram is obtained from which it is easy to read the hydrocarbon type to which a component belongs, or the chromatogram can be compared with a standard substance and the identity thus established.

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Résumé On décrit une méthode pour l'identification des carbures d'hydrogène à l'aide de ce que l'on appelle les spectres chromatographiques. Contrairement aux anciennes méthodes, dans lesquelles le composé à identifier se trouvait partagé dans 4 colonnes différentes montées en parallèle avec des phases stationnaires différentes puis il était de nouveau réuni après son passage dans un détecteur, ici, dans cette nouvelle variante, on opère de manière à ce que le composé organique passe d'abord à travers une colonne et ensuite à travers deux colonnes disposées en parallèle. On obtient un chromatogramme d'où l'on peut déduire très facilement à quel type de carbure d'hydrogène appartient un composant, et l'on peut comparer le chromatogramme avec celui d'une substance étalon et par suite, faire l'identification.

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Herrn Prof. Dr. Ing.M. Jureek zum 60. Geburtstag gewidmet.

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Vorgetragen anläßlich des V. Symposiums über Gaschromatographie in Berlin, Mai 1965.     

Proper holomorphic embeddings into stein manifolds with the density property

We prove that a Stein manifold of dimension d admits a proper holomorphic embedding into any Stein manifold of dimension at least 2d + 1 satisfying the holomorphic density property. This generalizes classical theorems of Remmert, Bishop and Narasimhan, pertaining to embeddings into complex euclidean spaces, as well as several other recent results.