Sensitive determination of free and plasma protein-bound dipyridamole by high-performance liquid chromatography

For many years dipyridamole (DP) has been used in the treatment of hypertension as a vasodilator, but recently it has been recognised as an anti-platelet aggregation agent and to potentiate anti-metabolite activity. A rapid and sensitive (20 nM) procedure for the determination of free and protein-bound DP in plasma, using reversed-phase high-performance liquid chromatography on an Ultrasphere XL ODS (3 microns) column (70 mm x 4.6 mm I.D.) with ultraviolet detection (280 nm), is reported. Free and bound DP were separated using ultrafiltration. Concentrations of DP between 0.1 and 10 microM were measured in plasma with a relative standard deviation of less than 9.6%. The subsequent determination of DP levels in patients orally administered 450 mg per day showed that DP binding to plasma protein is higher than 90%.     

3,7-Dioxaazelaamides as Ionophores for Lithium Ion Selective Liquid Membrane Electrodes

Lipophilic neutral carriers were synthesized which show Li⁺/Na⁺ selectivities of up to ca. 80 in highly lipophilic liquid membranes. The sensor membranes exhibit improved response times and increased lifetimes as compared to systems described earlier. They allow reliable measurements of Li⁺ in blood serum within the clinical concentration range. A 1:1 Li⁺/ionophore complex of one representative (N,N,N′,N′-tetracyclohexyl-5,5-dimethyl-3,7-dioxaazelaamide) has been prepared, and its structure was elucidated by X-ray analysis.     

Microchemical characterization of paintings — A case study

Summary The fundamental importance of scientific research for the preservation and restoration of works of art is uncontestable. The methods described in this paper, such as light microscopy, microchemical tests, emission spectroscopy, chromatography, scanning electron analysis, electron microprobe analysis and infrared spectroscopy, are of special significance in this filed. Nevertheless a better understanding of the problems that arise out of new special questions of art history can be obtained only by the right interpretation of the data obtained by scientific methods.

---

Mikrochemische Charakterisierung von Gemälden

Zusammenfassung Die grundlegende Bedeutung wissenschaftlicher Forschung für die Erhaltung und Restaurierung von Kunstwerken ist unbestritten. Die hier beschriebenen Methoden (Lichtmikroskopie, mikrochemische Reaktionen, Emissionsspektroskopie, Chromatographie, Rasterelektronen-Analyse und Infrarotspektroskopie) sind hierfür von zunehmender Bedeutung. Sie ermöglichen ein besseres Verständnis neuerer kunsthistorischer Probleme nur durch die richtige Interpretation der Ergebnisse wissenschaftlicher Methoden.

     

Automatische Analyse und Simulation von NMR-Spektren

Analytical and Bioanalytical Chemistry -     

Improved separation of palladium species in biological matrices by using a combination of gel permeation chromatography and isotachophoresis

The binding of palladium to high-molecular-mass compounds in palladium-treated lettuce is investigated as an example for a biological matrix. The total palladium concentration in lettuce leaves is 10.3 ng/g wet weight. After homogenization, high-molecular-mass compounds (> 10 kDa) are isolated by ultrafiltration. For separation of these palladium species a combination of preparative gel permeation chromatography (GPC) and preparative isotachophoresis (ITP) is used. Palladium is determined in separated fractions by using a highly sensitive total reflection X-ray fluorescence (TXRF) method after preconcentration. After GPC separation, four main fractions of palladium species are collected, each containing palladium in ng quantities (3-10 ng). Two of these fractions are further separated by ITP, yielding at least three main peaks per GPC fraction, each containing palladium in the range of 0.3-3 ng. These palladium containing peaks are characterized by high-performance size exclusion chromatography (HPSEC) and capillary isotachophoresis (cITP) in parallel. HPSEC enables the estimation of the molecular mass of six main palladium peaks, covering a molecular mass range of 69-200 kDa. It is also shown that the estimation of molecular mass after separation is more reliable than the respective estimation directly in the first GPC run. However, cITP reveals that each of the separated peaks is still a mixture of at least five different compounds.     

Etorphine‐Related Ferrocenyl‐Substituted Morphinan Alkaloids

The two diastereoisomeric ferrocenyl‐substituted orvinols 2 and 3 were prepared. The modified alkaloids are still able to interact with opioid receptors (see Table). The ferrocene moiety allows highly selective and sensitive electrochemical detection. The X‐ray crystal structure of the major isomer 2 was determined. The combination of a metallocene and a morphinan alkaloid holds promise for useful antitumor activity.