Atomic weight and absolute isotopic composition of a natural iron isotopic reference material

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:5655178

Maeck, R

The relatively poor knowledge of the isotopic composition and Atomic Weight of iron was one of the prime reasons for starting the work described in this thesis. The work presented here has ultimately led to significantly improved values for both these entities, and was obtained on a reference iron material using Thermionic Mass Spectrometry. Absolute determinations could be made as the mass spectrometer was calibrated using synthetic isotope mixtures. In total five mixtures were gravimetrically prepared from isotopically enriched [sup 54]Fe and [sup 56]Fe. After screening several compounds to the [alpha]-Fe[sub 2]O[sub 3] was selected as the carrier compound, as it was experimentally verified that its properties matched the requirements for preparing synthetic isotopes mixtures. In this [alpha]-Fe[sub 2]O[sub 3] the 2s uncertainty on the stoichiometry coefficient of iron was demonstrated to be at a level of 0.038%. Procedures based on semi-preparative chromatography were developed to purify these materials to a total impurity level of 100 [+-] 100 [mu]g/g (2s). The n([sup 54]Fe)In([sup 56]Fe) isotope abundance ratios in the mixtures varied from 0.1 to 10, with a relative 2s uncertainty on these prepared ratios of 0.02% to 0.07%. Various mass spectrometric procedures were developed to measure the isotope abundance ratios of the enriched materials, synthetic mixtures and the reference sample. For this, two spectrometers of different design were used, equipped with different detectors (Faraday/ion counter). In spite of the significant instrumental differences, the isotope abundance ratios for n([sup 54]Fe)In([sup 56]Fe) obtained on the natural iron reference sample agreed within 0.025%. This corroborates the statement that the new isotope abundance values and hence the Atomic Weight of this sample, are indeed absolute. The absolute isotopic composition and Atomic Weight thus obtained carry a significant smaller uncertainty compared to the existing IU-PAC data on iron.

• Research Organization: Universitaire Instelling Antwerpen, Antwerp (Belgium)
• OSTI ID: 5655178
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360104* -- Metals & Alloys-- Physical Properties
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
ABUNDANCE
CALIBRATION STANDARDS
CHROMATOGRAPHY
DISPERSIONS
ELEMENTS
IRON
ISOTOPE RATIO
MASS NUMBER
MASS SPECTRA
METALS
MIXTURES
SEPARATION PROCESSES
SPECTRA
STANDARDS
STOICHIOMETRY
TRANSITION ELEMENTS