Chiral separations by host-guest complexation with cyclodextrin and crown ether in capillary zone electrophoresis

Summary Capillary zone electrophoresis using cyclodextrins and a chiral crown ether as buffer constituents was studied for the enantiomeric separation of drugs and amino acids. Based on results obtained from separation of racemic -amino acids both chiral selectors are compared with respect to resolution, efficiency and retention time. For (±)-Quinagolide effects of buffer composition and temperature are examined using -cyclodextrin as chiral agent. Optimum conditions were pH 2.5 at 30 mmol L^–1 -cyclodextrin. A linear dependence of retention on -cyclodextrin concentration allowed calculation of formation constants of the host-guest complexes. Buffer concentration and temperature also influence resolution. The application of a chiral crown ether to the separation of optical isomers in capillary zone electrophoresis is described for the first time. Chiral recognition of solutes depends on the formation of protonated alkyl amines and separation is attributed to the formation of diastereomeric host-guest complexes with different interactions for each enantiomer. The effects of crown ether concentration on resolution are presented.     

Inclusive ϕ production inK − p interactions at 110 GeV/c and search for structure in φ π−

Results on inclusive ? production inK ^? p interactions at 110 GeV/c are presented. The production cross section is found to be larger than in πp andpp interactions at similar energies, suggesting OZI allowed \(s\bar s\) fusion to be the dominant mechanism in ? production. Thex distributions of ? and \(\bar K^{*0} \) are found to be similar to each other over the entirex range suggesting an overall strangeness suppression factor of 0.20±0.04 in the sea to be the dominant source of the difference in the cross section for ? and \(\bar K^{*0} \) . There is no evidence of a narrowφπ ^? state around 2.1 GeV/c² as suggested byK ⁺ experiments, but there is some excess of events in the region 1.94?1.98 GeV/c² consistent with theF-meson mass as observed ine ⁺ e ^? experiments.     

Über substituierte Bis-biphenylen-allyl-Radikale

Zusammenfassung Fluoren reagiert in Gegenwart starker Basen mit Biphenylenvinylbromiden vom Typ (Biph)C=C(R)-Br; dabei bilden sich unter Halogenwasserstoffabspaltung direkt die Anionen acider Propene, deren Entladung mit K₃Fe(CN)₆ sehr stabile Kohlenstoffradikale liefert. Die Dehydrierung des 1,4-Bis-[bis-biphenylen-propenyl-(2)]-benzols ergibt das Biradikal V. Die 2-Arylbis-biphenylen-allyl-Radikale liegen in Lösung und im Fest-zustand bis 77° K monomer vor; ihre Elektronen- und ihre ESR-Spektren wurden aufgenommen.     

The effect of bubbles on the measured electrochemical parameters during hydrogen evolution on nickel

The hydrogen evoluton reaction has been investigated at nickel rotating and vertical stationary electrodes in 1 M HC1. Steady state current—potential, impedance—potential and potential step—current—time transients results are reported. The impedance is analysed by equivalent circuit to produce double layr capacity—potential, ohrnic resistance—potential (and charge transfer resistance—potential) curves. Some deductions are made about the bubble layer and its effect on the electron transfer mechanism for the reaction.