Combination of matrix solid-phase dispersion extraction and direct on-line liquid chromatography-nuclear magnetic resonance spectroscopy-tandem mass spectrometry as a new efficient approach for the rapid screening of natural products: application to the total asterosaponin fraction of the starfish Asterias rubens

A combination of matrix solid-phase dispersion extraction (MSPD) and LC-NMR-MS hyphenation is proposed as a rapid screening method of natural products for unknown compounds. In this report, this new analytical approach is applied for the first time. MSPD represents a significant simplification compared to classical extraction procedures and is thus an excellent complement to the fast and powerful LC-NMR-MS: MSPD yields extracts suitable for LC-NMR-MS in one simple preparation step, while LC-NMR-MS yields a wealth of information in one single chromatographic run. The suitability of this technique to characterise glycosidic compounds in the molecular mass range of 1200 to 1400 a.m.u. is demonstrated. The information on the number of exchangeable protons provided by an additional back-exchange experiment proved to be particularly valuable for structural elucidation. The possibility of semi-quantitative LC-NMR measurements through methyl signals H(3)-18 and 19 of the steroidal skeleton is demonstrated and is ensuingly used to provide relative quantitative data of the steroid oligosaccharide fraction.     

Nucleophilic Addition to Acetylenes in Superbasic Catalytic Systems: XI. Transformations of Alkali Metal Hydroxides during Vinylation of 1-Heptanol with Acetylene under Elevated Pressure

Base-catalyzed addition of 1-heptanol to acetylene under elevated pressure of the latter is accompanied by side processes including formation of carboxylic acid salts (alkali metal heptanoates and acetates) with liberation of hydrogen and acetylene polymerization. The rate of acetylene absorption depends on the alkali metal nature and falls down in the series CsOH·H₂O RbOH·H₂O > 2KOH·H₂O > NaOH > LiOH. Approximately the same order is observed for variation of the rate of deactivation of the catalyst owing to its transformation into metal carboxylate. Dehydration of the catalyst accelerates both vinylation and acetylene polymerization.     

Short-Chain Branching in Polyethylene and Poly(vinyl Chloride) Using Pyrolysis Hydrogenation Gas Chromatography and 13C Nuclear Magnetic Resonance Analysis

This study compares the use of pyrolysis hydrogenation gas chromatography (PHGC) and ¹³C Fourier transform nuclear magnetic resonance (FTNMR) methods for the analysis of reference polyethylene (PE) samples, ethylene-α-olefin copolymers, and specially prepared poly(vinyl chloride) (PVC) samples which were reduced to their PE skeletal structures. The nature and relative quantities of the short branches along the polymer chains were determined using both techniques. Improved high-resolution PHGC data, obtained with a fused silica capillary separation column, gave results which were in satisfactory agreement with the ¹³C FTNMR data. This approach confirms that detailed microstructural information can be obtained with these methods by using carefully controlled experimental conditions and appropriate reference systems.     

Photon-assisted tunneling in a biased strongly correlated Bose gas

We study the impact of coherently generated lattice photons on an atomic Mott insulator subjected to a uniform force. Analogous to an array of tunnel-coupled and biased quantum dots, we observe sharp, interaction-shifted photon-assisted tunneling resonances corresponding to tunneling one and two lattice sites either with or against the force and resolve multiorbital shifts of these resonances. By driving a Landau-Zener sweep across such a resonance, we realize a quantum phase transition between a paramagnet and an antiferromagnet and observe quench dynamics when the system is tuned to the critical point. Direct extensions will produce gauge fields and site-resolved spin flips, for topological physics and quantum computing.     

Komplexometrische Phosphatbestimmung

Zusammenfassung Zink kann neben Phosphat komplexometrisch mit Eriochromschwarz T als Indicator mit sehr scharfem Endpunkt titriert werden. Aus dieser Tatsache ergibt sich die Möglichkeit einer maßanalytischen Phosphatbestimmung. Ammoniumzinkphosphat wird gefällt, ausgewaschen und wieder aufgelöst. In der Lösung wird Zink titriert. Voraussetzung für die Berechnung des Phosphatgehaltes ist die stöchiometrische Zusammensetzung des Ammoniumzinkphosphat-Niederschlags.Für die Bestimmung des Phosphatgehaltes wäßriger Lösungen von Phosphorsäure oder von Alkaliphosphaten werden Arbeitsvorschriften gegeben, die für den Makrobereich (200-25 mg), für den Halbmikrobereich (10-2,5 mg) und für den Mikrobereich (1,0-0,1 mg) gelten. Diese Arbeitsvorschriften unterscheiden sich im wesentlichen nur durch geänderte Volumina der benutzten Reagentien und der Ausgangslösung.Der Zeitbedarf für dieses Verfahren ist naturgemäß geringer als bei einem Verfahren mit gravimetrischer Endbestimmung. Das Verfahren ist für die Serienbestimmung geeignet. Über seine Anwendung zur Analyse phosphathaltiger technischer Produkte wird in einer weiteren Mitteilung berichtet werden.Die Untersuchung wurde mit Unterstützung der Deutschen Forschungsgemeinschaft durchgeführt.