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201.
Electroanalytical and chromatographic determination of pentachlorophenol and related molecules in a contaminated soil: a real case example 总被引:1,自引:0,他引:1
L. Codognoto V. G. Zuin D. de Souza J. H. Yariwake S. A. S. Machado L. A. Avaca 《Microchemical Journal》2004,77(2):177-184
Electroanalytical and chromatographic methodologies have been applied for the determination of pentachlorophenol (PCP) and some of its derivatives in real soil samples contaminated by industrial discharge. The analytes were extracted with hexane from soil samples collected at different points of the site and mixed to produce a representative sample. Square wave voltammetry (SWV) experiments were carried out on either a boron-doped diamond (BDD) electrode or a gold ultramicroelectrode (Au-UME) in an analyte composed by the Britton-Robinson (B-R) buffer at pH 5.5 with the direct addition of proper amounts of the extract. The voltammetric responses revealed an irreversible anodic peak at approximately 0.80 V vs. Ag/AgCl with a peak current showing a linear dependence on PCP concentration. This linear relationship yielded a detection limit (DL) of 2×10−8 mol l−1 (or 5.5 μg l−1) for the BDD electrode and 6.9×10−8 mol l−1 (18.4 μg l−1) for the Au-UME, while the independently measured HPLC detection limit was 1.1×10−8 mol l−1 (3.0 μg l−1). The application of electroanalytical and chromatographic methodologies in the analysis of soil extracts revealed, besides the PCP responses, signals for some related molecules such as o-tetrachlorobenzoquinone (o-chloranil), hexachlorobenzene and tetrachlorophenol. Recovering experiments for PCP showed a concentration of 27.5 mg kg−1 for the electroanalytical determinations and 26.8 mg kg−1 for the HPLC analysis, values exceedingly high if considering that the maximum residue limit established for natural waters by the Brazilian Environmental Agency is 10 μg l−1. 相似文献
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G. Frossati S. A. J. Wiegers T. Tata R. Jochemsen P. G. van de Haar L. P. Roobol 《Czechoslovak Journal of Physics》1990,40(8):909-926
The superfluid A1 an A2 transitions have been studied by means of vibrating wire viscosimeters in magnetic fields up to 9.3 T. Using the technique of quick melting of polarized solid (Castaing-Nozières effect) we have succeeded in increasing the superfluid transition temperature
from 2.86 to 3.23 mK, which is the highest up to now. Using this method, with some improvements, it should be possible to test some of the present theoretical models for3He. A minimum of the viscosity in the A1 phase has been observed for the first time. Very close to the A2 transition an anomaly in the amplitude of the viscometers seems to indicate the presence of a new phase, or some textural change due to dipole locking.Invited talk at the International Conference on Macroscopic Quantum Phenomena, Smolenice Castle, Czechoslovakia, September 18–22, 1989.The authors wish to thank C. C. Kranenburg and C. M. C. M. van Woerkens for their various contributions to the experiments. Very helpful discussions with K. S. Bedell, B. Castaing, H. Capel, P. Nozières, D. Rainer, A. Schakel, and G. A. Vermeulen are gratefully acknowledged. This work was financially supported by the Stichting voor Fundamenteel Onderzoek der Materie F. O. M. 相似文献
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