Filtern
Dokumenttyp
Schlagworte
- Acoustic levitation (3)
- High resolution (3)
- In-situ (3)
- SyXRD (3)
- Synchrotron radiation (3)
- X-Ray diffraction (3)
- Cement hydration (2)
- Crystallization (2)
- ELISA (2)
- LC-MS/MS (2)
Sulfamethoxazol (SMX),a sulfonamide, is a widely used bacteriostatic antibiotic and therefore a promising marker for the entry of anthropogenic Pollution in the environment. SMX is frequently found in wastewater and surface water. This study presents the production of high affinity and selective polyclonal antibodies for SMX and the development and Evaluation of a direct competitive enzyme-linked immunosorbent assay(ELISA)for the quantification of SMX in environmental watersamples. The crystal structures of the cross-reacting compounds sulfamethizole, N4-acetyl-SMX andsuccinimidyl-SMX were determined by x-ray diffraction aiming to explain their high cross-reactivity. These crystal structures are described for the first time. The quantification range of the ELISA is 0.82–63 µg/L. To verify our results, the SMX concentration in 20 environmental samples,including wastewater and surfacewater,was determined by ELISA and tandem mass spectrometry(MS/MS).A good Agreement of the measured SMX concentrations was found with average recoveries of 97–113%for the results of ELISA compared to LC-MS/MS.
Sulfamethoxazol (SMX),a sulfonamide, is a widely used bacteriostatic antibiotic and therefore a promising marker for the entry of anthropogenic Pollution in the environment. SMX is frequently found in wastewater and surface water. This study presents the production of high affinity and selective polyclonal antibodies for SMX and the development and Evaluation of a direct competitive enzyme-linked immunosorbent assay(ELISA)for the quantification of SMX in environmental watersamples. The crystal structures of the cross-reacting compounds sulfamethizole, N4-acetyl-SMX andsuccinimidyl-SMX were determined by x-ray diffraction aiming to explain their high cross-reactivity. These crystal structures are described for the first time. The quantification range of the ELISA is 0.82–63 µg/L. To verify our results, the SMX concentration in 20 environmental samples,including wastewater and surfacewater,was determined by ELISA and tandem mass spectrometry(MS/MS).A good Agreement of the measured SMX concentrations was found with average recoveries of 97–113%for the results of ELISA compared to LC-MS/MS.
Pathway of a damaging mechanism - Analyzing chloride attack by synchrotron based X-ray diffraction
(2015)
Typically, the changes of the phase compositions due to the chemical attack are studied in-situ only by chemical analysis or microscopy. In this study, the chloride transport and binding in the cement matrix in different cementitious materials was analyzed by synchrotron based X-ray diffraction (SyXRD) and energy dispersive X-ray spectroscopy (EDX). Sample materials consisting of cement paste were embedded in high concentrated sodium chloride solution over different time spans. Afterwards, the phase and chemical compositions were determined. The high spatial resolution and the information about the chloride distribution offer a detailed view of chloride binding in the cement matrix and allow the conclusions about the degradation mechanisms. The results are discussed related to the influence of different supplementary cementitious materials on the damaging mechanism.
Methods for the determination of boron in various matrices described in the literature usually employ complexing agents like mannitol to retain the volatile boron species during matrix evaporation steps. However, also relatively high boron recoveries from silicon containing samples have been reported when no complexing agents were added to the digestion acids. The mechanism behind this matrix-dependant recovery has been investigated by studying the boron recovery in the analysis of solar grade silicon. It was found that the NH4+ ion formed by the reduction of nitric acid during sample digestion is responsible for the higher recovery of boron, which leads to a possible analysis method without the use of complexing agents if the sample preparation procedure is carefully optimized.
Mechanochemical synthesis of [Zn3(C2O4)3(4,4'-bipy)4] and its reorganization at high temperatures
(2014)
The metal organic layered structure catena-(bis(µ2-4,4'-bipyridine)-tris(µ2-oxalato)-bis(4,4'-bipyridine)-tri-zinc(ii)) ([Zn3(C2O4)3(4,4'-bipy)4]) was synthesized mechanochemically applying three different routes. The synthesis succeeded by i) simultaneously neat grinding the three starting materials zinc acetate dihydrate, oxalic acid dihydrate and 4,4'bipyridine, ii) grinding two compounds and adding the third afterwards, independent of the sequence. The products were characterized using powder X-ray diffraction, Raman spectroscopy, gas adsorption measurements, and scanning electron microscopy. Temperature-dependent synchrotron XRD measurements revealed that the monoclinic structure of [Zn3(C2O4)3(4,4'-bipy)4] rearranges reversibly to a higher ordered orthorhombic structure [Zn(C2O4)(4,4'-bipy)] at high temperatures.
Spatially resolved analysis of complex multi-phase systems can be validated through different analytical methods. This study compares investigations by scanning electron microscopy coupled with energy dispersive X-ray fluorescence analysis and high resolution X-ray diffraction. The studied sulfate attacked cement paste containing fly ashes consists of different interacting crystalline and amorphous phases. The complementary methods revealed in detail changes in phase composition due to the chemical attack. The advantages and disadvantages of both methods are discussed and suggestions are given for combining them with additional methods to maximize the information content.
The formation and growth of hydroxylamine reduced silver nanoparticles were investigated by simultaneous Raman and UV/Vis spectroscopy coupled to an acoustic levitator as a sample holder. Based on the UV/Vis spectra, a two step particle formation mechanism with fast initial formation and adjacent coalescence can be proposed for the reduction of silver nitrate with hydroxylamine. The presence of the analyte adenine during particle formation resulted in differences in the adenine SERS signature compared to experiments, where adenine was added after particle synthesis. It was possible to monitor the adenine and sodium chloride induced aggregation of the nanoparticles and its dynamics based on both the extinction spectra and the SERS data. Correlating the information from the extinction spectra with the SERS intensity, the maximum SERS signals were observed at maximum extinction of the aggregated nanoparticle solution at the Raman excitation wavelength.
A systematic crystal morphology study on the pharmaceutical model compound caffeine has been conducted on different surfaces: silicon, silver, soda lime glass, and silver subsurface ion-exchanged soda-lime silicate (SIMO) glasses. The morphology of the solid caffeine deposits has been investigated using environmental scanning electron microscopy (ESEM), atomic force microscopy (AFM), and X-ray diffraction (XRD). Needle-shaped caffeine crystals have been observed by drop-casting and also by applying the rapid expansion of supercritical solutions (RESS) technique using supercritical carbon dioxide. The aspect ratio of the crystalline needles typically vary between 10 and 100, but have been observed as large as 500. The XRD data of the RESS products indicate unambiguously the presence of the thermodynamically most stable polymorph of caffeine known as the β-form. Under defined conditions we observe a unique, surface-mediated morphology for caffeine crystals with nearly perfect hexagonal shape. The relative fraction of the hexagons was seen to strongly increase especially when SIMO glasses were used. These hexagons have a distinct upper size limit depending on the solvent and substrate being used. The size distribution analysis of the hexagons yielded an average perimeter of typically 10 µm. The mechanism of the formation process of this new hexagonal motif is explained in terms of the spinodal dewetting of the thin film of caffeine solution on the surface.
Acoustic levitation represents the physical background of trapping a sample in a standing acoustic wave with no contact to the wave generating device. For the last three decades, sample holders based on this effect have been commonly used for contact free handling of samples coupled with a number of analytical techniques. In this study, a wall-free climate unit is presented, which allows the control of the environmental conditions of suspended samples. The insulation is based on a continuous cold/hot gas flow around the sample and thus does not require any additional isolation material. This provides a direct access to the levitated sample and circumvents any influence of the climate unit material to the running analyses.
Höchst dynamische Hydratationsprozesse in den ersten Sekunden bei der Entstehung eines Bauwerkes lassen sich mithilfe von Synchrotron-Röntgenbeugung mit einer sehr hohen Zeitauflösung nachverfolgen. Der Schwerpunkt lag dabei auf der Beeinflussung der Bildung erster kristalliner Hydratationsprodukte während des Frühstadiums der Zementhydratation.