Determination of Albuterol Enantiomers in Animal Tissue Matrices by LC–MS/MS: Application in Therapeutic Myoanabolic Studies

Albuterol (salbutamol) is a widely used medication in respiratory disease including asthma and chronic obstructive airways disease; however, like other beta2-agonists, it also exerts some extrapulmonary effects on muscle and fat. Surprisingly, there have been relatively few reports of albuterol tissue distribution, and the distribution of individual albuterol enantiomers into tissue has not been reported. The method presented here explores the use of an HPLC tandem mass spectrometry (LC–MS/MS) system (LTQ Orbitrap hybrid mass spectrometer) with deuterated standard and solid-phase extraction to determine low levels of albuterol enantiomers in tissue. The lower limit of quantification (LLOQ) was 0.156 ng g⁻¹, with a precision RSD <15% for both enantiomers. The assay was linear over the calibration range of LLOQ-10.0 ng g⁻¹ in muscle tissue (r ² > 0.98). The assay was successfully applied to pharmacokinetic studies in rats and mice. By utilizing a deuterated internal standard and LC–MS/MS detection, this assay can be used to measure albuterol enantiomers in muscle tissue. This assay has also identified that albuterol uptake appears to be stereoselective, and enantioselective assays are clearly warranted for myoanabolic studies involving administration of racemic-albuterol.

     

Surface-Enhanced Raman Scattering (SERS) of Nitrothiophenol Isomers Chemisorbed on TiO2

Surface-enhanced Raman scattering (SERS) spectroscopy and density functional theory (DFT) calculations were used to investigate the nature of the charge-transfer (CT) process between nitrothiophenol (NTP) isomers and the n-type semiconductor, TiO₂. The Raman signals of p-NTP and m-NTP that were chemisorbed onto TiO₂ were significantly enhanced with respect to their corresponding neat compounds. In particular, an enhancement factor (EF) of 10²–10³ was observed for both p-NTP and m-NTP, with m-NTP displaying a larger EF compared to p-NTP. The Raman signal of o-NTP on TiO₂ was not detectable, owing to interference from fluorescence emissions. A molecule-to-TiO₂ charge-transfer mechanism was responsible for the enhanced Raman signals observed in p-NTP and m-NTP. This transfer was due to a strong coupling between the adsorbate and the metal oxide, which led to an optically driven CT transition from the HOMO of NTP into the conduction band of TiO₂. Based on the mesomeric effect, the NO₂ group para to the thiol had a stronger electron-withdrawing ability than the NO₂ group at the meta position. A less-efficient CT transition from p-NTP to TiO₂ in the surface complex resulted in a weaker Raman-signal enhancement for p-NTP compared to m-NTP. The DFT calculation determined that the HOMO and the LUMO of NTP bound to TiO₂ were located entirely on the adsorbate and the semiconductor, respectively, thereby supporting the experimental findings that a molecule-to-TiO₂ mechanism was the driving force behind the observed SERS effect.     

Zum Nachweis und zur Bestimmung des Stickstoffs in organischen K?rpern

Ohne Zusammenfassung     

Spin-resolved inverse photoemission of ferromagnetic surfaces

Inverse photoemission (IPE) with spin-polarized electrons provides a way to measure separately the exchange-split majority and minority bands in ferromagnets above the Fermi level. Consequently spin-resolved IPE turns out to be an outstanding technique for obtaining information on surface magnetism: the magnetization of the topmost atomic layer may be investigated by measuring the exchange splitting of electronic states that are localized within the surface layer. Theoretical models of ferromagnetism may be tested by observing the temperature behavior of bands which contribute to the ferromagnetism of the material. The magnetic coupling of an adsorbate to the ferromagnetic substrate may be studied by probing adsorbate-induced bands. Results for the Ni(110) surface serve as an illustration to discuss the status of spin-resolved IPE and its application to the field of surface magnetism.     

Dynamic optimization of chemical cleaning in dead-end ultra filtration

In this paper a control strategy is formulated that minimizes the costs for a single chemical cleaning of a dead-end ultra filtration membrane. From the process model, the performance index and the constraints it can be derived that dynamic optimization will lead to a ‘maximum effort control problem’, in which the controls (cleaning flow and cleaning agent concentration) are either zero or maximum. The change from maximum to zero is called the switching point. This switching point depends on the overall cleaning time and the requested cleaning effectiveness. From the calculated optimal control strategy it follows that cleaning time can be significantly reduced, compared to conventional cleaning.     

Implementing pure adaptive search for global optimization using Markov chain sampling

The Pure Adaptive Search (PAS) algorithm for global optimization yields a sequence of points, each of which is uniformly distributed in the level set corresponding to its predecessor. This algorithm has the highly desirable property of solving a large class of global optimization problems using a number of iterations that increases at most linearly in the dimension of the problem. Unfortunately, PAS has remained of mostly theoretical interest due to the difficulty of generating, in each iteration, a point uniformly distributed in the improving feasible region. In this article, we derive a coupling equivalence between generating an approximately uniformly distributed point using Markov chain sampling, and generating an exactly uniformly distributed point with a certain probability. This result is used to characterize the complexity of a PAS-implementation as a function of (a) the number of iterations required by PAS to achieve a certain solution quality guarantee, and (b) the complexity of the sampling algorithm used. As an application, we use this equivalence to show that PAS, using the so-called Random ball walk Markov chain sampling method for generating nearly uniform points in a convex region, can be used to solve most convex programming problems in polynomial time.     

Beitrag zur Kenntniss des Kobalts

Ohne Zusammenfassung     

Zur Aufschliessung arsen- und antimonhaltiger Verbindungen

Ohne Zusammenfassung