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51.
Application of stir bar sorptive extraction for wine analysis 总被引:4,自引:0,他引:4
Yoji?Hayasaka Kevin?MacNamara Gayle?A.?Baldock Randell?L.?Taylor Alan?P.?PollnitzEmail author 《Analytical and bioanalytical chemistry》2003,375(7):948-955
Stir bar sorptive extraction (SBSE) coupled with gas chromatography/mass spectrometry (GC/MS) was used to analyse wine samples for three applications: flavour and compositional analysis; 2,4,6-trichloroanisole (TCA), a common off-aroma in wine; and agrochemicals. SBSE was found to be orders of magnitude more sensitive than modern conventional methodology, allowing for lower detection and quantitation levels, and improved confirmation of identity; SBSE often gave better signal to noise in scan mode than other methods in selective ion monitoring (SIM) mode. With the help of their characteristic mass spectra all agrochemicals could be identified unambiguously at concentrations of 10 microg L(-1) in wine and a further 100 constituents were detected in a Cabernet Sauvignon sample. Thus it is now possible to analyse complex samples such as wine by scan mode, with better confirmation of identity, and without sacrificing sensitivity, where previously SIM methodology had to be used. 相似文献
52.
J. B. Campbell J. M. Greene E. R. Lavagnino D. N. Gardner A. J. Pike J. Snoddy E. C. Taylor 《Journal of heterocyclic chemistry》1986,23(3):669-672
New methods of preparing 2,3-diaminopyridine ( 13 ) from 2-chloro-3-nitropyridine ( 11 ) and 3,4-diaminopy-ridine ( 8 ) from 4-ethoxy-3-nitropyridine hydrochloride ( 5 ) have been explored and evaluated. 相似文献
53.
R. C. Heaton W. A. Taylor D. R. Phillips Sr. D. J. Jamriska J. B. Garcia 《Journal of Radioanalytical and Nuclear Chemistry》1995,195(2):271-277
Zinc oxide targets irradiated with high energy protons at the Los Alamos Meson Physics Facility (LAMPF) contain a number of radioactive spallation products in quantities large enough to warrant recovery. This paper describes methods for recovering7Be,46Sc, and48V from such targets and offers suggestions on possible ways to recover additional isotopes. The proposed methods are based on traditional precipitation and ion exchange techniques, are readily adaptable to hot cell use, and produce no hazardous waste components. The products are obtained in moderate to high yields and have excellent radionuclidic purity. 相似文献
54.
The crystal structures of α-UF5 and U2F9 were refined with high-resolution neutron powder diffraction data from an mixture. Refinement was achieved by a multiphase Rietveld profile refinement technique. The results are compared with previous X-ray and neutron powder studies. 相似文献
55.
Rabindra N. Roy Lakshmi N. Roy Jason G. Grant Mason P. Cummins Bennett J. Tabor III Sarah J. Richards Curtis A. Himes Bret R. Lively Penny L. Blackwell Ashley N. Simon 《Journal of solution chemistry》2002,31(11):861-872
The values of the second dissociation constant, pK
2, for the dissociation of the NH+ charge center of the zwitterionic buffer compounds 4-(N-morpholino)butanesulfonic acid (MOBS), and N-(2-hydroxyethyl)piperazine-N-4-butanesulfonic acid (HEPBS) have been determined from 5 to 55°C, including, 37°C at intervals of 5°C. The electromotive-force (emf) measurements have been made utilizing hydrogen electrodes and silver–silver chloride electrodes. The value of pK
2 for MOBS was found to be 7.702 ± 0.0005, and 8.284 ± 0.0004 for HEPBS, at 25°C, respectively. The related thermodynamic quantities, G
o, H
o, S
o, and C
p
o for the dissociation processes of MOBS and HEPBS have been derived from the temperature coefficients of pK
2. Both the MOBS and HEPBS buffer materials are useful as primary pH standards for the control of pH 7.3 to 8.6 in the region close to that of physiological fluids. 相似文献
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We report the first high pressure129I Mössbauer measurements with elemental iodine at pressures to 30 GPa. A 20 mg/cm2
129I2 absorber was mounted in a diamond anvil cell with an effective diameter of 0.21 mm. The source used was Mg3
129mTeO6. Experiments were performed mainly at 4 K and the pressure was monitored by the ruby fluorescence method. With increasing pressure we observe a gradual decrease in ¦e2qQ¦ and an increase in IS and values of the low pressure, molecular phase; at 16 GPa a new phase (HP1) is detected characterized by a change in sign of e2qQ and a smaller value of ¦e2qQ¦, and a substantial increase in . At 24 GPa a new phase (HP2) is formed that is characterized by a smaller value of . In general the population of the molecular phase decreases from 1.0 near 15 GPa to a value of 0.4 at 30 GPa. The fraction of the high pressure phase (HP1 + HP2) increases at the expense of the molecular phase and that of the HP2 at the expense of the HP1 phase. These observations are discussed in relation to the onset of a metallic phase near 16 GPa and recent x-ray diffraction studies.Work performed under the auspices of the U.S. Department of Energy. 相似文献