Efficient analyte oxidation in an electrospray ion source using a porous flow-through electrode emitter

This article describes the components, operation, and use of a porous flow-through electrode emitter in an electrospray ion source. This emitter electrode geometry provided enhanced mass transport to the electrode surface to exploit the inherent electrochemistry of the electrospray process for efficient analyte oxidation at flow rates up to 800 microL/min. An upstream current loop in the electrospray source circuit, formed by a grounded contact to solution upstream of the emitter electrode, was utilized to increase the magnitude of the total current at the emitter electrode to overcome current limits to efficient oxidation. The resistance in this upstream current loop was altered to control the current and "dial-in" the extent of analyte oxidation, and thus, the abundance and nature of the oxidized analyte ions observed in the mass spectrum. The oxidation of reserpine to form a variety of products by multiple electron transfer reactions and oxidation of the ferroceneboronate derivative of pinacol to form the ES active radical cation were used to study and to illustrate the performance of this new emitter electrode design. Flow injection, continuous infusion, and on-line HPLC experiments were performed.     

Fully automated liquid extraction‐based surface sampling and ionization using a chip‐based robotic nanoelectrospray platform

A fully automated liquid extraction‐based surface sampling device utilizing an Advion NanoMate chip‐based infusion nanoelectrospray ionization system is reported. Analyses were enabled for discrete spot sampling by using the Advanced User Interface of the current commercial control software. This software interface provided the parameter control necessary for the NanoMate robotic pipettor to both form and withdraw a liquid microjunction for sampling from a surface. The system was tested with three types of analytically important sample surface types, viz., spotted sample arrays on a MALDI plate, dried blood spots on paper, and whole‐body thin tissue sections from drug dosed mice. The qualitative and quantitative data were consistent with previous studies employing other liquid extraction‐based surface sampling techniques. Published in 2009 by John Wiley & Sons, Ltd.     

The size of irregular points for a measure

For a measure μ on the complex plane μ-regular points play an important role in various polynomial inequalities. In the present work it is shown that every point in the set {μ′>0} (actually of a larger set where μ is strong) with the exception of a set of zero logarithmic capacity is a μ-regular point. Here “set of zero logarithmic capacity” cannot be replaced by “β-logarithmic Hausdorff measure  0” with β=1 (it can be replaced by “β-logarithmic measure 0” with any β>1). On the other hand, for arbitrary μ the set of μ-regular points can be quite small, but never empty.     

Ueber die Trennung des Fuchsins vom Orseillefarbstoff

Ohne Zusammenfassung     

Properties of Sizeable [n]Cycloparaphenylenes as Molecular Models of Single‐Wall Carbon Nanotubes Elucidated by Raman Spectroscopy: Structural and Electron‐Transfer Responses under Mechanical Stress

[n]Cycloparaphenylenes behave as molecular templates of “perfectly chemically defined” single‐wall carbon nanotubes. These [n]CPP molecules have electronic, mechanical, and chemical properties in size correspondence with their giant congeners. Under mechanical stress, they form charge‐transfer salts, or complexes with fullerene, by one‐electron concave–convex electron transfer.     

Charge shift bonding concept in radical π-dimers

We show that pancake bonding in radical π-dimers display features of charge shift (CS) bonding. While the CS bonding concept has been developed to interpret the unusual aspects of σ-bonds around centers with a large number of lone pairs, such as F(2) and HOOH, we find a similar role played by the nonbonding or slightly bonding π-electron pairs in π-stacking radical dimers. Arguments and computational evidence indicate that the CS bonding concept developed by Shaik and Hiberty et al. captures essential features of the intermolecular bonding in radical π-dimers in which the overlap of the two radical centered singly occupied molecular orbitals (SOMOs) play a crucial role. By using the tetracyanoethylene anion dimer, [TCNE](2)(2-), as a model, we show that compared to CAS(2,2) calculations, significant binding contributions are recovered in the calculations simply by including selected intrapair excitations of the SOMO-SOMO bonding orbitals and the nonbonding π-orbitals. This observation is the basis for the analogy of chemical bonding between pancake bonded radical π-dimers and other charge shift bonded molecules, such as F(2). By extending the CS bonding concept to a new class of molecules, we find a novel application of the lone pair bond weakening effect (LPBWE) in which the doubly occupied π-orbitals play the role of lone pairs.