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  • 1995-1999  (4)
  • 1998  (4)
  • 1
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermal ionization isotope dilution mass spectrometry (TI-IDMS) was used as an oligo-element method for the determination of Cr, Cd and Pb in photographic AgCl emulsions. After addition of an appropriate amount of isotopically enriched spikes (53Cr, 116Cd and 206Pb) to the solid samples, the latter were completely dissolved in NH3 solution, permitting isotopic exchange to take place. Thereafter, AgCl was selectively removed by precipitation, whereby ultrasonic treatment was used to enhance the recovery of the elements of interest. Despite the use of concentrated HNO3 and H2O2 during further sample processing, preliminary experiments indicated the presence of a substantial remainder of the organic matrix (gelatine). Hence, the analytes of interest were isolated by means of electrolytic deposition on Pt electrodes. Subsequently, the deposits were dissolved from the Pt electrodes using a mixture of concentrated HNO3 and H2O2 and the solutions evaporated to dryness. The solid residues were taken up in diluted HNO3 and loaded onto Re filaments. In order to improve the ionization yield, prior to the sample, a silicagel suspension containing AlCl3 was loaded onto the filament and after sample loading, both H3BO3 (for Cr and Pb) and H3PO4 (for Cd and Pb) were added as further ionization aids. Finally, the isotope ratios of interest (52Cr/53Cr, 114Cd/116Cd and 206Pb/208Pb) were determined using thermal ionization mass spectrometry, whereby all three analyte elements were vaporized from the same filament. The limits of detection obtained using this procedure range from 0.4 ng (for Cd) to 4 ng (for Pb). Four different AgCl emulsions were analyzed. For Cr, the concentration found was quite similar for all emulsions analyzed, as it varied between ∼ 40 and ∼ 100 ng/g only. For Cd, very low values were found for all samples analyzed (≤ 3 ng/g). Finally, for Pb a much larger variation from ∼ 10 ng/g up to ∼ 5.5 μg/g was observed. For the sample with the highest Pb content, an excellent agreement could be established between the results obtained using quadrupole-based ICP-IDMS and those using TI-IDMS. For the determination of Cr by means of quadrupole-based ICP-IDMS, an instrument equipped with a ShieldTorch system was used to avoid spectral overlap of the 52Cr+ and 40Ar12C+ ion signals. Also in this case, the results obtained are in very good agreement with those obtained using TI-IDMS. The comparison between TI-IDMS and ICP-IDMS also made clear that sample inhomogeneity limits the between-sample precision attainable.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0517
    Keywords: Key words Trace elements ; Water ; Intercomparison ; Comparability ; Traceability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract  The sixth round of the International Measurement Evaluation Programme (IMEP) is presented. The programme offers reference values, established by primary methods of measurement, against which participating laboratories can evaluate their performance. The degree of comparability is thus established against the most objective references available at present. In IMEP-6, reference values for total concentrations of 14 trace elements in a synthetic and a natural water were established mainly by isotope dilution mass spectrometry (IDMS). For the majority of the measurands, results traceable to the international system of units (SI) and having expanded uncertainties, U (k=2), of 2% could be established. Measurements results from 165 field laboratories in 29 countries are evaluated and presented as descriptive (regional, national and intercontinental) pictures of the participants' self-declared degree of experience, status of accreditation, performance (including target values for uncertainty set by authorities) and instrumental methods used. The participants' use of certified reference materials and calibrants has been documented, and some comments on this matter are raised. The results and characteristics for IMEP-6 are compared with those of IMEP-3 (1991–1993) and discussed in view of the forthcoming IMEP-9 (1998).
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report efficient room-temperature continuous-wave intracavity frequency doubling of an upconversion-pumped Er(1%):YLiF4 laser at 850 nm. A titanium–sapphire laser was used for excitation of the 4S3/2→4I13/2 transition in erbium. The maximum laser output power at 850 nm was 1200 mW. Intracavity frequency doubling the fundamental wave utilizing lithium triborate as nonlinear crystal yielded a maximum second-harmonic output power of 540 mW at 425 nm. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Publication Date: 1998-01-01
    Print ISSN: 0026-461X
    Electronic ISSN: 1471-8022
    Topics: Geosciences
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