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1.
Supercritical fluid extraction (SFE) with CO(2), a clean and rapid alternative to conventional organic solvent extraction techniques, was investigated for the extraction of 2,4-D from soils using a variety of pre-extraction soil treatments to enhance extraction recoveries. Initial experiments with silylation, ion-pairing, methyl esterification, and ionic displacement are reported. Methyl esterification and ionic displacement during SFE proved to be the most promising approaches for quantitative extraction. Although the SFE procedures were not fully optimized, comparison between SFE and a standard Soxhlet extraction method demonstrated the potential for improving analytical measurement for highly polar pesticides in soil by modifying SFE-CO(2) extraction with derivatizing reagents and ionic solutions. 相似文献
2.
A sensitive method for the accurate determination of phytic acid in food samples is described. The proposed procedure involves the anion-exchange liquid chromatography with conductivity detection. Initially, two methods of determination of phytic acid were compared: absorptiometry and high-performance ion chromatography (HPIC) with chemically suppressed conductivity detector. Unlike most conventional methods involving precipitation by FeCl3, the simpler and more reliable HPIC assay avoids the numerous assumptions inherent in the iron precipitation and the accuracy is independent of the phytate content. The protocol was also applied to a survey of phytic acid concentration in some cereal, oil and legume seeds. 相似文献
3.
Yang DQ Rochette JF Sacher E 《Langmuir : the ACS journal of surfaces and colloids》2005,21(18):8539-8545
The chemical and morphological modifications of multiwalled carbon nanotubes (MWCNTs), by 2 keV Ar(+) treatment, have been followed by field emission scanning (FESEM) and high-resolution transmission (HRTEM) electron microscopies and by X-ray photoelectron (XPS) and Raman spectroscopies. Morphological changes were followed, both in situ and on subsequent air exposure, and the data indicate that free radical defects, initially produced under low Ar(+) treatment doses ( approximately 10(13) ions/cm(2)), act as the nuclei for the formation of localized asperities that form along the walls of the CNTs. Continued treatment results in their stublike elongation that continues with further treatment, forming extensions under heavy treatment doses. The chemical changes that occur, on reaction with air, reveal that the defects initially created are secondary C atoms, formed when a single bond breaks; further treatment breaks an additional bond to form primary C atoms; free radical fragments, lost when the third bond breaks, condense on the free radical defects to form the asperities. The extent of primary and secondary C atoms, and thus their functionalization on air exposure, may be controlled by the extent of treatment, offering a method for the controlled surface functionalization of CNTs by low-energy Ar(+) treatment. 相似文献
4.
The operation of a polarization-mode dispersion monitor insensitive to chromatic dispersion is demonstrated at 40 Gbits/s. The high-speed processing device is based on the Kerr effect and provides an optical power output as a reading of differential group delay. The monitor is compatible with return-to-zero modulation formats at data rates in excess of 40 Gbits/s and does not require the use of high-data-rate electronics. 相似文献
5.
Florian Modicom Ellen M. G. Jamieson Elise Rochette Stephen M. Goldup 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(12):3915-3919
We report the unexpected discovery of a tandem active template CuAAC‐rearrangement process, in which N2 is extruded on the way to the 1,2,3‐triazole product to give instead acrylamide rotaxanes. Mechanistic investigations suggest this process is dictated by the mechanical bond, which stabilizes the CuI‐triazolide intermediate of the CuAAC reaction and diverts it down the rearrangement pathway; when no mechanical bond is formed, the CuAAC product is isolated. 相似文献
6.
Pascal Sonnet Sophie Da NascimentoDanielle Marty Nicolas FranceschiniJean Guillon Jean-Daniel BrionJacques Rochette 《Tetrahedron letters》2003,44(16):3293-3296
The first synthesis of two segetalins B and G is described. The corresponding linear peptides were synthesized using standard automated continuous-flow SPPS methods. Ring closure positions were investigated for segetalin B. The best ring closure result was obtained between Val and Gly. 相似文献
7.
Isolation of human haemoglobin variants with altered Bohr effect. Application to haemoglobin Rainier
Isoelectric focusing on polyacrylamide gel in the absence of haem ligands represents a useful, convenient and rapid procedure to isolate silent Hb variants in their native forms, provided that they exhibit an abnormal Bohr effect. The amount of material which is eluted is sufficient for both a limited functional study and a structural determination using microscale high-performance liquid chromatography. This is exemplified by the isolation and the study of Hb Rainier. 相似文献
8.
Sreenath Bolisetty Sabine Rosenfeldt Christophe N. Rochette Ludger Harnau Peter Lindner Youyong Xu Axel H. E. Müller Matthias Ballauff 《Colloid and polymer science》2009,287(2):129-138
We present a systematic study of flexible cylindrical brush-shaped macromolecules in a good solvent by small-angle neutron
scattering (SANS), static light scattering (SLS), and by dynamic light scattering (DLS) in dilute and semi-dilute solution.
The SLS and SANS data extrapolated to infinite dilution lead to the shape of the polymer that can be modeled in terms of a
worm-like chain with a contour length of 380 nm and a persistence length of 17.5 nm. SANS data taken at higher polymer concentration
were evaluated by using the polymer reference interaction site model (PRISM). We find that the persistence length reduce from
17.5 nm at infinite dilution to 5.3 nm at the highest concentration (volume fraction 0.038). This is comparable with the decrease
of the persistence length in semi-dilute concentration predicted theoretically for polyelectrolytes. This finding reveals
a softening of stiffness of the polymer brushes caused by their mutual interaction. 相似文献
9.
J. Marfaing P. Rochette J. Pellerey P. Chaurand C. Suavet L. Folco 《Journal of magnetism and magnetic materials》2008
A collection of iron-rich micrometeorites from Antarctica have been investigated using electron spin resonance (ESR) and conventional magnetic methods to establish a complete magnetic codification of their specific characteristics. Due to the high selectivity of the ESR, the spectra show that the amount and nature of the magnetic impurities contained in these tiny-sized samples, mainly Ni and Cr ions, significantly modify their ESR responses. This result provides a criterion, the Ni/Cr content (identified by spectroscopy), useful for a faithful classification of this class of extraterrestrial particles with close magnetic properties. We attempt to separate the contribution of the different magnetic ions in the ESR response. This method can be easily extended to other magnetic impurities. 相似文献
10.
R. Boulay R. Gagnon D. Rochette J. R. Izatt 《International Journal of Infrared and Millimeter Waves》1984,5(9):1221-1234
Measurement of several parameters pertinent to process and quality control in the manufacture of paper products is a potentially important application of far-infrared lasers. Preliminary measurements of the transmittance and reflectance of moist paper sheets are presented, and their use to determine the percentage moisture content and the dry basis weight of the paper is discussed. 相似文献