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  • 1
    Electronic Resource
    Electronic Resource
    L-subshell Coster-Kronig yields for Tb (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 24 (1995), S. 221-225 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The synchrotron photoionization method was applied to measure L-subshell Coster-Kronig yields for Tb. This method is based on the capability of tuning the energy of the synchrotron photons producing a selective subshell ionization. A foil sample of Tb was irradiated and characteristic spectra were recorded. Data were analysed using a new formalism (based on a matrix representation) to express x-ray fluorescence intensities involving Coster-Kronig transitions. The results obtained were f12 = 0.201 ± 0.014, f13 = 0.281 ± 0.027 and f23 = 0.097 ± 0.016. These data represent valuable information for spectroscopists, considering the lack of data for L-shell parameters.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300240502
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  • 2
    Electronic Resource
    Electronic Resource
    Electron impact mass spectrometry of praziquantel derivativesContribution No. 1049 from Instituto de Quimica, UNAM. (1991)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 26 (1991), S. 503-504 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electron impact mass spectra of a series of compounds related to the anthelmintic substance praziquantel are described in sufficient detail to permit their assay in biological samples by selected ion monitoring.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210260524
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  • 3
    Electronic Resource
    Electronic Resource
    A comparison of two equations used as calibration curves for ternary samples in x-ray fluorescence spectrometry (1982)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 11 (1982), S. 66-69 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: It is well known that calibration curves in x-ray fluorescence spectrometry offer to the analyst different alternatives to fit measured data. We have set out to compare two well-known algorithms, those of Rasberry and Heinrich (R-H) and Lachance and Traill modified by Claisse and Quintin (LTCQ), with computer generated data using the fundamental parameter method. It is seen that both work reasonable well for binary samples, but in ternary samples deviations from reference points are larger for R-H than for LTCQ. We conclude from this study that ternary effects in R-H are not accounted for adequately, since only binary coefficients are needed to determine a calibration curve for any ternary as well as any multicomponent sample. In LTCQ, inclusion of an additional coefficient determined from a ternary standard suffices to improve considerably the degree of fitting to reference.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300110208
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  • 4
    Electronic Resource
    Electronic Resource
    Quantification of dideoxycytidine in human plasma by gas chromatography/mass spectrometry (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 17 (1988), S. 399-404 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A gas chromatographic/mass spectrometric procedure has been developed for the quantification in plasma of dideoxycytidine (DDC), a candidate anti-AIDS drug. The assay uses an extraction with ethyl acetate containing 10% methanol followed by three derivatization steps: (i) reaction with t-butyl dimethyl chlorosilane to silylate the 5′-hydroxyl group; (ii) pentafluorobenzoylation of the amino group with pentafluorobenzoyl chloride; (iii) methylation of the ring nitrogen adjacent to the amino group with diazomethane. The resulting derivative is quantified using stable isotope dilution, selective ion monitoring and methane negative chemical ionization mass spectrometry. Plasma concentrations of DDC were measured over a range of 2-200 ng ml-1 using 1 ml plasma for extraction.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200170509
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  • 5
    Electronic Resource
    Electronic Resource
    A GC/MS Method for Determining UV Stabilizers in Polyethyleneterephthalate Bottles (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 317-320 
    Details
    ISSN: 0935-6304
    Keywords: GC/MS analysis ; SIM mode ; UV stabilizers ; PET ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Chemical characterization of ozonated lignin solutions from corn (Zea mays) stalk and poplar (Populus deltoides) wood by capillary gas chromatography (1997)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 20 (1997), S. 565-568 
    Details
    ISSN: 0935-6304
    Keywords: Capillary GC ; GC-MS ; Corn stalk and poplar wood lignins ; Ozone ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Corn (Zea mays) stalk and poplar (Populus deltoides) wood lignin was converted into monomeric aromatic compounds and short chain aliphatic carboxylic acids. The main reaction products were separated and identified using capillary gas chromatography-mass spectrometry on an HP-5 column. The compounds were considered as positively identified when their mass spectra and GC retention times agreed with those of authentic standard samples. The quantitative estimation of the identified reaction products was accomplished on an OV-101 capillary column by gas chromatography-FID using the internal standard method. Among the aromatic compounds, aldehydes (p-hydroxybenzaldehyde, vanillin, and syringaldehyde), acids (p-hydroxybenzoic, vanillic, 3,4-dihydroxybenzoic, and syringic), and one phenol (hydroquinone) were determined. In addition, the aliphatic carboxylic acids: glycolic, oxalic, malonic, glyoxylic, butanedioic, glyceric, and malic acid were identified. All the calibration curves of the quantified compounds approximated to a straight line. For both corn stalk and poplar wood lignins, the major components were the aromatic aldehydes (71 and 64% of the characterized fraction, respectively), followed by the aliphatic carboxylic acids (20 and 21% of the characterized fraction, respectively).
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240201009
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  • 7
    Electronic Resource
    Electronic Resource
    L-subshell fluorescence yields measured with synchrotron radiation (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 23 (1994), S. 267-271 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The synchrotron photoionization method was applied to measure L-subshell fluorescence yields. This method is based on the capability of tuning the energy of the synchrotron photons producing a selective subshell ionization. Three foil samples of Tb, Ho and Yb were irradiated and their characteristic spectra were recorded. Although it was not possible to obtain absolute results for the three ωL1, ωL2 and ωL3 fluorescence yields, the poorly known ωL1 and ωL2 coefficients were calculated using theoretical values for the well known ωL3 yield. The results are very reliable and agree with reported theoretical and experimental data. These coefficients are valuable information for spectroscopists considering the lack of data for L1- and L2-subshell parameters. Finally, synchrotron radiation has proved to be a useful tool for fundamental parameter determinations.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300230607
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  • 8
    Electronic Resource
    Electronic Resource
    Dependence of XRF intensity on the tilt of the propagation planeThis work was carried out within the general framework of a research project sponsored by the University of Cordoba, the Nation-al Research Council of Argentina (CONICET) and the Research Council of Cordoba Province (CONICOR). (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 18 (1989), S. 281-290 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A particular parameterization of both the incident and the take-off angles in the narrow beam model of the x-ray fluorescence (XRF) intensity, is introduced. The angles are related to the tilt α of the propagation plane (the plane defined by the incident and emerging beam's directions) and the XRF intensity is studied as a function of α.An interesting geometrical property of XRF is revealed. The primary XRF intensity remains invariant when α changes whereas the secondary and tertiary XRF intensities show a monotonic decrease when α increases. They vanish for the maximum tilt of α = π4 2. The different behaviours of the primary intensity on the one hand and the higher orders of XRF on the other allow the isolation of the primary emission. This would not otherwise be possible because the photons under the same spectral line come from all the emission orders. As they have the same energy, they cannot be resolved by the detection system.The theoretical predictions were confirmed experimentally. Measurements were made with a specially built device. Because of the difftculties of measuring near-horizontal emission, the limit-angle intensity is determined by extrapolation from intensity measurements at several α. As an example, primary emission of two NBS stainless-steel standards was obtained. Isolation of the secondary emission is also possible where higher orders are not involved.The fundamentals of this phenomenon may be better understood with the help of a Monte Carlo simulation of the XRF emission from finite slabs, embedded in the infinite target. The simulation shows the strong dependence of the layer emission on α. This result makes it possible to suggest that the angle a may be used as α ‘tuner’ of radiation coming from a given depth.Some practical applications of this geometrical property of XRF intensity are discussed. The intensity change due to a slight tilt of the propagation plane (i.e. a sample improperly placed in the sample holder), is found to besmall. Also, two spectrochemical methods of analysis benefiting from the composition dependence of the reduced intensity and the selective emission from different depths applied to the thickness gauge of thin samples are con-sidered.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300180608
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  • 9
    Electronic Resource
    Electronic Resource
    Determination of ωγ using the tilt of the propagation plane (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 22 (1993), S. 89-91 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The product of fluorescence yield (ω) and emission probability (Γ), was measured using a method based on the propagation plane inclination. Measurements of the Kα line of elements such as Cr, Fe and Ni on binary samples were carried out to determine the product ωΓ. The results were compared with those reported in well known compilations. The proposed procedure can be considered a new alternative to increase the available set of methods for measuring fundamental parameters.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300220207
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  • 10
    Electronic Resource
    Electronic Resource
    Dependence of XRF intensity on the tilt of the propagation plane: Experimental (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 20 (1991), S. 163-169 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The geometrical properties of the x-ray fluorescence (XRF) intensity related to the α-parameterization were confirmed experimentally. A special sample stage was built to allow the rotation of the sample with the propagation plane (the plane defined by the incident and take-off beam directions) and was coupled to an energy-dispersive spectrometer. The device and the way in which it was carefully aligned with the collimated x-ray beams are described. The fluorescence spectra of three NBS standard samples were measured for 16 different positions of the α angle. The incident and take-off angles were both 45° for sample rotations between α = 0 and the maximum angle of 86°. XRF intensities from non-enhanced lines do not show any dependence on α as predicted by theory. Enhanced lines, on the contrary, decrease in intensity when α increases, allowing the isolation of the primary emission by extrapolation to the limiting case α = π/2.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300200403
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