Filtern
Erscheinungsjahr
Dokumenttyp
- Zeitschriftenartikel (179)
- Vortrag (46)
- Beitrag zu einem Tagungsband (10)
- Beitrag zu einem Sammelband (3)
- Sonstiges (2)
- Posterpräsentation (1)
Schlagworte
- LIBS (13)
- ICP-MS (12)
- ELISA (8)
- LC-MS/MS (8)
- Laser ablation (8)
- Acoustic levitation (7)
- Speciation (7)
- Traceability (6)
- Calibration (5)
- Characterization (5)
Organisationseinheit der BAM
- 1 Analytische Chemie; Referenzmaterialien (32)
- P Präsident (29)
- P.0 Präsident und andere (29)
- 1.1 Anorganische Spurenanalytik (15)
- 6 Materialchemie (12)
- 6.3 Strukturanalytik (8)
- 1.6 Anorganische Referenzmaterialien (6)
- 1.7 Organische Spuren- und Lebensmittelanalytik (6)
- 1.8 Umweltanalytik (5)
- 6.1 Oberflächen- und Dünnschichtanalyse (5)
Eingeladener Vortrag
- nein (46)
For the investigation of small sample volumes, the use of an acoustic levitator was tested as a `sample holder' for hovering droplets in a synchrotron beam. It might be advantageous to use levitated droplets instead of samples confined in solid holders, especially for the study of crystallization processes where the influence of containing walls has to be minimized. In a first experiment, the crystallization of sodium chloride in a small droplet of aqueous solution has been followed with a time resolution of 30 s. The collected diffraction peaks are compared with data in the ICSD database.
Gated detection with intensified detectors, e.g., ICCDs, is today the accepted approach for detection of plasma emission in laser-induced breakdown spectroscopy (LIBS). However, these systems are more cost-intensive and less robust than nonintensified CCDs. The objective of this paper is to compare, both theoretically and experimentally, the performance of an intensified (ICCD) and nonintensified (CCD) detectors for detection of plasma emission in LIBS. The CCD is used in combination with a mechanical chopper, which blocks the early continuum radiation from the plasma. The detectors are attached sequentially to an echelle spectrometer under the same experimental conditions. The laser plasma is induced on a series of steel samples under atmospheric conditions. Our results indicate that there is no substantial difference in the performance of the CCD and ICCD. Signal-to-noise ratios and limits of detection achieved with the CCD for Si, Ni, Cr, Mo, Cu, and V in steel are comparable or even better than those obtained with the ICCD. This result is further confirmed by simulation of the plasma emission signal and the corresponding response of the detectors in the limit of quantum (photon) noise.
Asymmetrical flow field-flow fractionation (AF4) was applied to characterize aquatic colloids from biological sewage plants and to infer information of colloidal loads, sources, and sinks within the plants, resp. the colloidal interaction with the aqueous phase and the sewage sludge. To characterize the colloids further, especially the distributions of colloid associated heavy metals, the AF4 system was coupled to an inductively coupled plasma mass spectrometer (ICP-MS). The size distribution is determined by AF4 with UV absorbance and fluorescence detection after a calibration by monodisperse polystyrene sulfonate standards (PSS). Samples from different sewage plants and from different depths and locations within a plant were compared. The fulvic/humic acid fraction with a particle diameter dp < 10 nm appeared to be comparable in all samples and decreases only slightly along the plants, whereas larger colloids with dp > 10 nm almost completely passed into the sewage sludge. The concentrations of the initial colloidal heavy metals decreased along the plants.
The stable carbon and nitrogen isotopic composition of urine and milk samples from cattle under different feeding regimes were analysed over a period of six months. The isotope ratios were measured with isotope ratio mass spectrometry (IRMS). The δ13C values of milk and urine were dependent on different feeding regimes based on C3 or C4 plants. The δ13C values are more negative under grass feeding than under maize feeding. The δ13C values of milk are more negative compared to urine and independent of the feeding regime. Under grass feeding the analysed milk and urine samples are enriched in 13C relative to the feed, whereas under maize feeding the 13C/12C ratio of urine is in the same range and milk is depleted in 13C relative to the diet. The difference between the 15N/14N ratios for the two feeding regimes is less pronounced than the 13C/12C ratios. The δ15N values in urine require more time to reach the new equilibrium, whereas the milk samples show no significant differences between the two feeding regimes.