Filtern
Dokumenttyp
- Zeitschriftenartikel (11)
- Beitrag zu einem Tagungsband (8)
- Vortrag (3)
Schlagworte
- Quantitative NMR (3)
- Atrazine (1)
- Cineole (1)
- Crystal structure (1)
- Ethanol (1)
- FT/IR (1)
- Fourier-Transform-Infrarot-Spektroskopie (1)
- GC-FID (1)
- Gehaltsbestimmung (1)
- H-1-Kernresonanz-Spektroskopie (1)
- H-1-NMR (1)
- Impurities (1)
- Infrared spectroscopy (1)
- Kapillargaschromatographie-Flammenionisationsdetektion (1)
- MKW (1)
- Metrology (1)
- Mineralölkohlenwasserstoffe (1)
- Monitor signal (1)
- NMR (1)
- Primary methods (1)
- Purity (1)
- Purity assessment (1)
- Quantitative analysis (1)
- Raman spectroscopy (1)
- Reference methods (1)
- Round robin test (1)
- Signal Intensities (1)
- Solid state NMR (1)
- Structure analysis (1)
- Tetrachlorinedecaoxide (TCDO) (1)
- Umweltanalytik (1)
- Uric acid monohydrate (1)
- Urinary calculus (1)
- Validation (1)
- Wasserunterdrückung (1)
- X-ray diffraction (1)
Eingeladener Vortrag
- nein (3)
Raman spectroscopic and 35Cl-NMR scans of Hydro-Xan®, a preparation containing the biocatalytically effective Tetrachlorinedecaoxide anion (TCDO), are described. The spectroscopic analyses showed that HydroXan® does not contain chlorite initially used in the preparation anymore. Furthermore, a structure of four equal chlorate-like ClO3-groups was indicated for TCDO by the scans. Such a structure is supported by the long-term stability of HydroXan® found at tests over 267 days.
The short- and long-term structural evolution and aging of solgel materials prepared under mild conditions are studied by fluorometry, dynamic light scattering (DLS), 29Si NMR and gravimetry. In combination with the first, a newly developed donoracceptor-substituted fluorescent probe with two acidophilic sites of different strength and topology is introduced. Its performance in detecting changes in parameters such as polarity, proticity, and pore volume on the microscopic scale is compared to two other dyes and to the macroscopic changes revealed by DLS, NMR and gravimetry. At early stages of the solgel process, fluorometry, DLS and NMR reveal similar changes which are typical of the structural evolution of SiO2 sols having different synthesis parameters. During later times of sol aging, DLS and NMR reflect the growth of the network and indicate that all sols approach similar structural equilibria. Fluorometry supports these findings by signalling a gradual decrease in mobile species with high proton activity. The formation of the spanning cluster upon gelation is strongly evident only from DLS results while the local environment of the fluorophore remains largely unchanged. However, the fluorescent dye is able to report microscopic changes even during long-term aging. Drying of the gels with a pronounced contraction of solvated pores is readily observable by fluorometry and gravimetry. During the late reaction stages, the fluorescence properties of the tailor-made dye are still sensitive toward the environment.
In our laboratory more than 100,000 urinary calculi have been analysed since 1972. Amongst this huge sample, 15 specimens originating from a total of eight patients were observed showing similar characteristics but escaping unambiguous identification with any of the substances that have been described so far in urinary concrements. Therefore, the unknown substance was submitted to a more extended analytical regimen. Structural analysis by x-ray crystallography turned out to be most successful, identifying the unknown material as uric acid monohydrate. Uric acid monohydrate crystallizes in the monocline space group P21/c. Within the crystal, uric acid and water molecules form continuous layers by hydrogen bonds. This is in contrast to uric acid in its water free and its dihydrate forms, which both crystallize by forming 3-dimensional networks To the best of our knowledge , the existence of a monohydrate form of uric acid has not been reported so far. Accordingly, this is the first report on uric acid monohydrate as a urinary stone component. The frequency of only 0.015% in our survey indicates that uric acid monohydrate is rarely the main component in concrements, in contrast to uric acid and uric acid dihydrate with frequencies of 10% and 6%, respectively. The infrared spectrum of uric acid monohydrate is very similar to that of the other crystal forms of uric acid. Because of this similarity and its low frequency, uric acid monohydrate may have been overlooked as a component of urinary concrements. X-ray diffraction allows for better differentiation in routine stone analysis. All samples of uric acid monohydrate were found by solid state NMR spectroscopy to be highly contaminated by amorphous material. This material consisted of long aliphatic chains reminiscent of lipids and fatty acids, respectively. Concrements consisting of other forms of uric acid or urate lacked this amorphous component. Therefore, a role of this aliphatic material has to be taken into consideration when discussing the conditions that may favour the rare formation of concrements from uric acid monohydrate. As for as the metabolic situation of the affected patients is concerned, no common peculiarities became evident by a retrospective survey.