Investigation on technetium species in ground water and migration through clay columns

Speciation of technetium in ground water has been studied for understanding the migration behaviour of this radionuclide in deep geological formations. A combination of free-liquid electromigration, ion exchange, solvent extraction, coprecipitation and dialysis methods has been applied. Both oxic and anoxic conditions have been employed. Systems studied include leaching of sodium borosilicate glass spiked with⁹⁹Tc and^95mTc followed by its passage through glauconitic sand columns, and dialysis of TcO₂ with ground water, sodium chloride, and humic acid solutions. Results indicate the presence of the pertechnetate, TcO ₄ ⁻ , ion as the dominating species.     

Synthesis of 3H-labeled Efomycine M

For in-depth characterization as a putative pan-selectin antagonist 3H-labeled Efomycine M was synthesized starting from the natural product derived from Elaiophyline.     

Organoplatinum-Bridged Cyclotribenzylene Dimers

Cyclotribenzylenes (CTBs) combining carbonitrile (−CN) and alkyne (−C₂H) substituents were synthesized as racemic mixtures and resolved by HPLC on chiral stationary phases. Two of these compounds were used to prepare platinum-bridged CTB dimers, in which Pt^II is bound to the CTBs via Pt−alkynyl bonds in cis configuration. The organometallic complexes were examined by mass spectrometry and NMR spectroscopy, which indicated that they were obtained as mixtures of diastereoisomers (a meso or syn form and a pair of chiral or anti forms) when racemic CTBs were used. Enantiomerically pure complexes were prepared from resolved CTBs, which allowed us to distinguish the NMR signals of the chiral and meso forms in the diastereoisomeric mixtures. In certain conditions, the platinum complexes played the role of a pincer π-alkynyl ligand for Cu(I) coming from the copper iodide used as a synthetic auxiliary. The Cu⁺ cations could be easily removed by treatment with NaCN, affording the mononuclear bis-cyclotribenzylene complexes. These compounds failed to lead to metallo-cryptophanes by coordination of two [M(dppp)]²⁺ complex subunits (M=Pd, Pt; dppp=1,3-bis(diphenylphosphino)propane), each to two carbonitrile substituents belonging to different CTBs, pointing to the superiority of the one pot self-assembly processes for the preparation of metallo-cryptophanes.     

An interface between the universal force field and the effective fragment potential method

In order to properly describe reactions in heterogeneous catalyst systems, the reactants, solvent, and bulk effects of the surface must be taken into account. Embedded-cluster QM (quantum mechanics)/MM (molecular mechanics) methods can treat reactions on surfaces (the gas-surface interface), and the effective fragment potential method (EFP) can accurately treat the solvent effects on reactions (the gas-liquid interface). In order to create a QM/MM/EFP hybrid method for treatment of heterogeneous catalytic systems in the presence of a solvent (the liquid-surface interface), an EFP-MM interaction potential has been developed. Example calculations on small clusters of silica and water have been carried out.     

Dünnschichtchromatographische Untersuchungen an Cyclohexanon-peroxiden

Zusammenfassung 1,1-Dihydroxydicyclohexyl-peroxid (I) und 1-Hydroxy-1-hydroperoxy-dicyclohexyl-peroxid (II) werden beim Aufbringen auf Schichten aus Kieselgel-G Merck vollständig nach Cyclohexanon und Wasserstoffperoxid bzw. nach Cyclohexanon und 1,1-Dihydroperoxy-cyclohexan (II a) aufgespalten. Die einfachen Additionen von Hydroperoxyverbindungen an Cyclohexanon werden bei Berührung mit dem katalytisch wirkenden Kieselgel rückgängig gemacht: auf der Platte lassen sich nur die Spaltungsprodukte nachweisen. Der hydrolytische Austausch von Hydroperoxy-gegen Hydroxygruppen kommt mit merklicher Geschwindigkeit erst bei der Einwirkung von Mineralsäure zustande. Auch auf acetyliertem Papier dürften I und II nicht beständig sein. Die aus I in Essigsäure als Lösungsmittel in Gegenwart des Ionentauschers Amberlite IR 120 (saure Form) entstehenden Peroxide lassen sich auf der Platte voneinander trennen. Die wichtigsten von diesen konnten identifiziert werdenl. Die entwickelten Untersuchungsmethoden eignen sich allgemein zur Reinheitsprüfung von Cyclohexanonperoxiden und zur Verfolgung ihrer Reaktionen.     

Determination of chlorophenols in urine of children and suggestion of reference values

During the course of a human biomonitoring project (Biebesheim in Hessen, Germany) we elaborated a simple but sensitive method for the determination of tri- (TCP), tetra- (TeCP) and pentachlorophenol (PCP) in human urine. Urine samples, spiked with internal standards, were treated by acid hydrolysis. After a steam bath distillation the distillates were extracted using solid phase extraction. Derivatization of the chlorophenols was not carried out. GC/ECD system was used for detection. Detection limits of the chlorophenols were found in the range of 0.02 μg/L urine (detection limits of the ECD: 0.52 to 2.76 μg/L). By this method mono- and dichlorophenols cannot be detected. We investigated 24h-urine samples of 339 pupils (age 10 to 12 years). The children live either in the surroundings of a hazardous waste incinerator (SVA) in Biebesheim (n = 193), or controls (i.e. regions without waste incinerator) in the non polluted areas of Odenwald (n = 90) and Rheintal (n = 56). Between these three groups we did not find statistically significant differences in chlorophenol concentrations of the urine samples. The 95-percentiles of the analyzed samples are 0.74 μg/L (2,3,4-TCP), 1.24 μg/L (2,3,5-TCP), 0.70 μg/L (2,3,6–TCP), 1.10 μg/L (2,4,5–TCP), 1.74 μg/L (2,4,6–TCP), 2.84 μg/L (3,4,5–TCP), 4.78 μg/L (2,3,4,5-TeCP), 1.86 μg/L (2,3,4,6-TeCP), 2.90 μg/L (2,3,5,6-TeCP) and 4.39 μg/L (PCP). Received: 24 February 1999 / Revised: 3 May 1999 / Accepted: 6 May 1999     

Gold nanoparticles decorated with oligo(ethylene glycol) thiols: protein resistance and colloidal stability

The interactions between proteins and gold colloids functionalized with protein-resistant oligo(ethylene glycol) (OEG) thiol, HS(CH2)11(OCH2CH2)6OMe (EG6OMe), in aqueous solution have been studied by small-angle X-ray scattering (SAXS) and UV-vis spectroscopy. The mean size, 2R, and the size distribution of the decorated gold colloids have been characterized by SAXS. The monolayer-protected gold colloids have no correlations due to the low volume fraction in solution and are stable in a wide range of temperatures (5-70 degrees C), pH (1.3-12.4), and ionic strength (0-1.0 M). In contrast, protein (bovine serum albumin) solutions with concentrations in the range of 60-200 mg/mL (4.6-14.5 vol %) show a pronounced correlation peak in SAXS, which results from the repulsive electrostatic interaction between charged proteins. These protein interactions show significant dependence on ionic strength, as would be expected for an electrostatic interaction (Zhang et al. J. Phys. Chem. B 2007, 111, 251). For a mixture of proteins and gold colloids, the protein-protein interaction changes little upon mixing with OEG-decorated gold colloids. In contrast, the colloid-colloid interaction is found to be strongly dependent on the protein concentration and the size of the colloid itself. Adding protein to a colloidal solution results in an attractive depletion interaction between functionalized gold colloids, and above a critical protein concentration, c*, the colloids form aggregates and flocculate. Adding salt to such mixtures enhances the depletion effect and decreases the critical protein concentration. The aggregation is a reversible process (i.e., diluting the solution leads to dissolution of aggregates). The results also indicate that the charge of the OEG self-assembled monolayer at a curved interface has a rather limited effect on the colloidal stabilization and the repulsive interaction with proteins.