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411.
Flórez Menéndez JC Fernández Sánchez ML Fernández Martínez E Sánchez Uría JE Sanz-Medel A 《Talanta》2004,63(4):809-814
The determination of five volatile organochlorine compounds, VOX (chloroform, 1,1,1-trichloroethane, carbon tetrachloride, trichloroethene and tetrachloroethene) in raw landfill leachates and biologically cleansed leachates by GC-MS is investigated. Two extraction and preconcentration procedures were evaluated for recovery of such analies from the samples, including static headspace (HS) and solid phase microextraction by sampling the headspace above the sample (HS-SPME). Optimisation of operating parameters for the best performance of both, sampling and preconcentration techniques was described. Detection limits, time of analysis, precision and linear ranges of both introduction techniques have been established. Application of proposed methods to the determination of the five VOX under study in the above referred samples revealed the absence of such analytes in both leachates. Then both methods were applied to the determination to the five organochlorine compounds under study on spiked leachates samples. While HS-GC-MS offered better analytical precision than HS-SPME-GC-MS, this last technique gave a faster analytical response because no dilution must be done for a reliable VOX determination in landfill leachates. In any case, both sample introduction techniques tested provides excellent recoveries and good analytical precision (ranged from 1 to 3%). 相似文献
412.
Ejaz ur Rehman Riffat Naheed Shakeel ur Rehman Munir Ahmed 《Journal of Radioanalytical and Nuclear Chemistry》2007,273(2):333-336
The precision in measurement of trace level uranium isotopic ratio, i.e., 236U/238U or 234U/238U, on single Faraday detector with narrow dynamic range is very hard to achieve. this is mainly due to the narrow dynamic
range of a single detector systems. A significant improvement in mass spectrometric determination of 236U/238U ratio has been achieved by employing an alternate method using a single Faraday detector of narrow dynamic range. The method
makes use of the precise measurements of the 236U/234U ratio, 234U/235U ratio and 235U/238U ratio, which are used to calculate the 236U/238U ratio using the equation 236U/238U=236U/234U×234U/235U×235U/238U. Despite the fact that correlation of the data tends to increase the uncertainty in the result, our results show a significant
improvement, i.e., more than 8 times better precision in measuring the 236U/238U ratio with this method (σ=3.98×10−08) as compared to direct measurement of 236U/238U (σ=3.104×10−07). The method widens the applicability of the single collector system with narrow dynamic range and it will potentially be
helpful to improve the precision in the case of the static multi-collector system also. The objective of the present study
was to compare the results of the same sample analyzed with the present alternate method and the direct method for precision. 相似文献
413.
W. Rehman M. K. Baloch A. Badshah S. Ali 《Russian Journal of Coordination Chemistry》2005,31(12):856-860
The synthesis and study of new coordination compounds of some organotin(IV) chlorides with monomethyl glutarate are reported. The ligand molecule appears to be bound to the tin atom through the carboxylic oxygen. The results obtained from 1H, 13C, and 119Sn NMR, FT-IR and 119Sn Mossbauer spectra show that the complexes are pentacoordinated with the trigonal bipyramidal structure. Biological screening of organotin(IV) derivatives shows promising activity, especially for the triphenyltin complex exhibiting higher antifungal activity. In addition, the rest of the compounds also prove to be active against various fungi used. 相似文献
414.
Interactions of polyvinylpyrrolidone (PVP) with metal chlorides (MgCl2, CaCl2, KC1 and BaC12) have been investigated by viscometric and spectrophotometric techniques in aqueous solutions. Intrinsic viscosity [η] of (PVP) has shown a discontinuity with varying concentration of metal chlorides. The decreasing order of effectiveness of cation is K1 >Ca2 > Mg2 > Ba2 for poly(vinylpyrrolidone) solution. Changes in the absorption spectra of the cosolutes were observed in the presence of PVP in the lower limit of the UV-visible region i.e. 200-210 nm. These changes were attributed to interaction of PVP molecules with the cosolute molecules. As the concentration of the cosolute increased, a red shift in the peaks was observed, indicating an increase in interaction between PVP and cosolutes. 相似文献
415.
A rapid, simple and accurate spectrophotometric method is developed for the determination of ondansetron hydrochloride in pure and tablet formulations. The method depends on the charge‐transfer complexation between ondansetron base as n‐electron donor with chloranil as π‐acceptor to give a colored complex, which absorbs maximally at 470 nm. Beer's law is obeyed in the concentration ranges 70–980 μg mL?1 with molar absorptivity of 4.47 × 102 L mole?1 cm?1. The proposed method is precise, accurate and specific for the quantitative determination of drug in bulk and tablet formulations. 相似文献
416.
D. Bucurescu C. A. Ur D. Bazzacco C. Rossi-Alvarez P. Spolaore C. M. Petrache M. Ionescu-Bujor S. Lunardi N. H. Medina D. R. Napoli M. De Poli G. de Angelis F. Brandolini A. Gadea P. Pavan G. F. Segato 《Zeitschrift für Physik A Hadrons and Nuclei》1995,352(4):361-362
High spin states have been observed for the first time in the odd-odd nucleus80Y, by using the24
Mg(58
Ni,pn) reaction at 180 MeV. Eight rotational bands have been established, indicating a nucleus with appreciable deformation.Supported by CNPq, Brazil 相似文献
417.
We explain Fermi acceleration of particles bouncing in a gravitational field and experiencing a force due to a modulated evanescent laser field. The acceleration strongly depends upon the initial conditions in the phase space and certain modulation amplitude. We study the accelerated modes by the Poincaré surface of sections and Lyapunov exponents. Furthermore, we identify the initial areas of the phase space that support accelerated dynamics and write a mapping for accelerated dynamics. We show that a distinction between accelerated and chaotic evolutions can be made with the help of the aspect ratio. The Lyapunov exponent shows that the accelerated mode supports ordered evolution. 相似文献
418.
Wajid Rehman Musa Kaleem Baloch Amin Badshah 《Russian Journal of Inorganic Chemistry》2007,52(1):102-107
The results of an investigation into the fungicidal properties of some organotin(IV) compounds with Mono-methyl phthalate are reported. The compounds were characterized by various spectroscopic techniques including 1H-13C-119Sn-NMR, FT-IR, and 119Sn Mössbauer studies. On the basis of these techniques, all the complexes show penta coordination with a trigonal bipyramidal environment around the tin. The synthesized compounds were tested against a number of plant pathogenic fungi. The fungicidal data reveal that the tri-phenyltin(IV) compound proves to be a powerful fungicide. Comparison between the fungicidal activity of the trialkyltin(IV) compounds shows that the tri-phenyl tin(IV) complex is most active against all plant pathogens; the rest of the complexes also exhibit significant antifungal activity but less than the former one. 相似文献
419.
420.
Adriaan M. H. van der Veen Milena Horvat Radmila Milačič Tinkara Bučar Urška Repinc Janez Ščančar Radojko Jaćimović 《Accreditation and quality assurance》2001,6(6):264-268
A proficiency test (PT) was carried out to investigate the quality of laboratory results measuring trace elements in sewage sludge. The scheme relied on reference values, established through flame atomic absorption spectroscopy and instrumental neutron activation analysis. Within the framework of the project, ”Proficiency testing in Central and Eastern European Countries”, the measurements were done in parallel using induced coupled plasma mass spectrometry. This paper discusses the design of the PTS, the metrological concepts behind it and the way in which it was operated. The discussion includes the estimation of measurement uncertainty of the reference values obtained, homogeneity testing and its uncertainty evaluation, as well as all relevant quality assurance aspects. From the results, it can be concluded that all measurement methods involved agree within their respective uncertainties. Furthermore, it can be concluded that it is feasible to operate a proficiency test of trace elements in sewage sludge using reference values. The agreement between the reference values and the consensus values is satisfactory. 相似文献