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81.
Clauwaert KM Van Bocxlaer JF Major HJ Claereboudt JA Lambert WE Van den Eeckhout EM Van Peteghem CH De Leenheer AP 《Rapid communications in mass spectrometry : RCM》1999,13(14):1540-1545
This paper describes the investigation of the potential of a quadrupole orthogonal acceleration time-of-flight mass spectrometer (Q-TOF) equipped with an atmospheric pressure ionisation interface for quantitative measurements of small molecules separated by reversed phase liquid chromatography. To this end, the detection limits and linear dynamic range in particular were studied in an LC/MS/MS experiment using 3,4-methylenedioxymethamphetamine standards and 3,4-methylenedioxyethylamphetamine for internal standardisation. In a second phase, the experiment was repeated with real biological extracts (whole blood, serum, and vitreous humour). A calibration for 3,4-methylenedioxymethamphetamine and its metabolite 3,4-methylenedioxyamphetamine was prepared in each of these matrices again using 3,4-methylenedioxyethylamphetamine as internal standard. The resulting quantitative data were compared with those obtained by liquid chromatography with fluorescence detection for the same extracts. The Q-TOF results revealed excellent sensitivity and a linear dynamic range of nearly four decades (2-10 000 pg on-column, r(2) = 0.9998, 1/x weighting). Furthermore, all the calibration curves prepared in biological material were superimposable, LC/MS/MS and LC-fluorescence, and the quantitative results for actual samples compared very favourably. It was concluded that the Q-TOF achieves a linear dynamic range for quantitative LC/MS/MS work exceeding that of fluorescence detection and at much better absolute sensitivity. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
82.
83.
With the aid of isotope labeling and by substituent shifts, the relatively strong m/z 91 ion in the mass spectra of 7-chloro-2-methoxy-5-phenyl-3H-1,4-benzodiazepine and related compounds was shown to contain the 5-phenyl ring and the 3-CH2 group. Mechanisms involving the opening of the 7-membered ring and the migration of the phenyl ring from C-5 to C-3 are postulated for the formation of this ion. This rearrangement ion was also observed in the mass spectra of some 1-alkyl-7-chloro-1,3-dhydro-5-phenyl-2H-1,4-benzodiazepin-2-ones. 相似文献
84.
Photonuclear activation and high resolution gamma-ray spectrometry have been used to determine non-destructively the concentrations of 25 trace elements in Maroccan phosphate rock. The activation was simultaneously performed for phosphate samples and multielement standards in the bremsstrahlung beam of a linear electron accelerator at 18 and 30 MeV maximum energies. Gamma-ray spectra were recorded with a 79 cm3 Ge(Li) detector and a programmable analyzer IN 96. A detailed study of interferences was carried out. Limits of detection between 0.5 and 125 μg·g?1 were obtained. 相似文献
85.
Fractional Linear Multistep Methods for Abel-Volterra Integral Equations of the First Kind 总被引:1,自引:0,他引:1
Fractional powers of linear multistep methods are suggestedfor the numerical solution of weakly singular Volterra integralequations of the first kind. The proposed methods are convergentof the order of the underlying multistep method. The stabilityproperties are directly related to those of the multistep method. 相似文献
86.
We estimate the growth order in n of the Taylor coefficientsof bounded univalent functions in the unit disk. Our estimatedepends on the norm of the Grunsky operator. In particular,we improve the known results for coefficients of quasiconformallyextendible univalent functions. 1991 Mathematics Subject Classification30C50, 30C75, 30C55. 相似文献
87.
I.A. Sellin S.B. Elston J.P. Forester P.M. Griffin D.J. Pegg R.S. Peterson R.S. Thoe C.R. Vane J.J. Wright K.-O. Groeneveld R. Laubert F. Chen 《Physics letters. A》1977,61(2):107-110
A study of Ne L-shell vacancy production by S~14+, Cl~12+ ions has shown copious production of NeIINeVIII excited states with ~10?18 cm2 cross sections and recoil velocities which may permit significantly higher resolution spectroscopy than is possible with beam-foil methods. 相似文献
88.
89.
M.P. Combes P. Berthet R. Frascaria CH.F. Perdrisat B. Tatischeff N. Willis J. Banaigs J. Berger A. Codino J. Duflo F. Plouin E. Aslanides F. Hibou O. Bing R. Beurtey M. Boivin D. Hutcheon Y. Le Bornec J. Yonnet 《Nuclear Physics A》1984,431(4):703-712
A search for isoscalar dibaryonic resonances by means of missing-mass spectra in the d + d → d + X reaction has been attempted using deuteron beams of T = 2.29,2.00 and 1.65 GeV. The results do not show any evidence for a narrow peak with a limit of for a 15 MeV width or a broad enhancement which could be unambiguously attributed to a dibaryonic resonance. 相似文献
90.
Abdallah MA Vane CR Havener CC Schultz DR Krause HF Jones N Datz S 《Physical review letters》2000,84(2):278-281
The stability of nonlinear laser light filaments in a homogeneous isothermal plasma with respect to coupled electromagnetic and density perturbations is examined. In addition to the previously known modulational instability of a trapped electromagnetic mode, a new fast growing resonant instability is found. It corresponds to the growth of an excited eigenmode in the waveguide formed by the filament density depletion, the associated density response being supersonic and transversally localized. The evolution of the instability is illustrated by numerical simulations in two and three spatial dimensions. 相似文献