The graft polymerization of e-caprolactone (e-CL) onto magnetite was carried out under microwave irradiation in the presence of tin(II) 2-ethylhexanoate. The molar ratio of e-CL to tin(II) 2-ethylhexanoate was 300, whereas the molar ratio of e-CL to magnetite was 5. The chemical structures of the obtained poly(e-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.

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.

No abstract

A highly sensitive method for the determination of gadolinium based MRI contrast agents in environmental water samples has been developed using hydrophilic interaction chromatography (HILIC) coupled with inductively coupled plasma mass spectrometry (ICP-MS). The contrast agents used in the present study are Gd-DTPA (Magnevist), Gd-DTPA-BMA (Omniscan), Gd-DOTA (Dotarem), Gd-BOPTA (Multihance) and Gd-BT-DO3A (Gadovist) which represent both classes of linear and macro cyclic and also ionic and non ionic contrast agents. A study of various parameters responsible for the efficient separation was performed and resulted in an optimum mobile phase composition of 20 mmol L À1 ammonium acetate in 60/40 ACN/water mixture at a flow rate of 0.1 mL min À1 in combination with a micro concentric type PFA nebuliser and ICP-MS detection of the 158 Gd isotope. All contrast agents have shown excellent linearity between 0.1 mg L À1 and 100 mg L À1 (R 2 > 0.99) for each MRI contrast agent with RSD values found to be less than 2% for triplicate measurements. The limit of quantification (LOQ) for all contrast agents were found to be less than 100 ng L À1 which allows the developed method to be employed in environmental trace analysis. Enrichment of water samples for the determination of contrast agents was performed by using a surface evaporation approach. The developed method has been applied successfully for the separation and determination of contrast agents in surface and waste water treatment plant samples. The MRI agent speciation results were compared with ICP-MS measurements for the total Gd concentrations.