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In view of its intended use as a sample for proficiency testing or as a reference material the stability of the extractable trace element contents of a soil from an irrigation field was tested using the extraction with 1 mol/L ammonium nitrate solution according to DIN 19730. Therefore, changes of the extractability of sterilized and non sterilized soil samples stored at different temperatures were evaluated over a period of 18 months. Sets of bottles were kept at -20 °C, +4 °C, about +20 °C and +40 °C, respectively. The NH4NO3 extractable contents of Cd, Cr, Cu, Ni, Pb and Zn were determined immediately after bottling and then after 3, 6, 12 and 18 months with ICP-AES or ETAAS. Appropriate storage conditions are of utmost importance to prevent deterioration of soil samples prepared for the determination of NH4NO3 extractable trace element contents. Temperatures above +20 °C must be avoided. The observed changes in the extractability of the metals (especially for Cr and Cu) most likely could be related to thermal degradation of the organic matter of the soil. There is no need to sterilize dry soil samples, because microbiological activity in soils with a low moisture content appears to be negligible with regard to trace element mobilization.
Entwicklung und Herstellung von Boden-Referenzmaterialien für die anorganische Umweltanalytik
(2000)
Validation of a European standard for the determination of hexavalent chromium in solid material
(2007)
A European standard for the determination of Cr(VI) in solid material has been elaborated in the framework of an international co-operation and finally validated in the course of an interlaboratory comparison. The procedure is based on the alkaline digestion prescribed by EPA method 3060A followed by ion chromatography and determines an operationally defined content of Cr(VI), including water-soluble and insoluble chromates. A preliminary robustness study was carried out in order to compare different extraction methodologies and to study the equivalency of different analytical methods for the determination of Cr(VI) in alkaline extracts of soil and waste materials. During an interlaboratory validation trial with 19 European laboratories a set of 4 samples (2 soil and 2 waste samples) was analysed to determine performance characteristics for different combinations of digestion and detection methods. With the procedures prescribed by the new European standard (EN 15192) acceptable results were obtained for both soil samples and one of the waste samples (sludge). However, for the second waste sample (fly ash) a large deviation in analytical results was observed. This indicates that particularly for waste materials a possible occurrence of strong matrix effects has to be considered and supplementary quality control data are needed in order to assess the validity of analytical results. The accuracy of the determination of Cr(VI) in solid matrices remains a challenging field in terms of maximum extraction efficiency and minimum species interconversion.
The graft polymerization of ε-caprolactone (ε-CL) onto magnetite was carried out under microwave irradiation in the presence of tin(II) 2-ethylhexanoate. The molar ratio of ε-CL to tin(II) 2-ethylhexanoate was 300, whereas the molar ratio of ε-CL to magnetite was 5. The chemical structures of the obtained poly(ε-caprolactone) coated magnetic nanoparticles were characterized by FTIR and XPS spectroscopy. These magnetic-polymer hybrid nanostructures were further investigated by X-ray diffraction and magnetization measurements. The morphology of the magnetic core-shell nanostructures were determined by TEM.