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TitleVaporization and atomization of uranium in a graphite tube electrothermal vaporizer: a mechanistic study using electrothermal vaporization inductively coupled plasma mass spectrometry and graphite furnace atomic absorption spectrometry
AuthorGoltz, D M; Grégoire, D C; Byrne, J P; Chakrabarti, C L
SourceSpectrochimica Acta, Part B: Atomic Spectroscopy vol. 50B, no. 8, 1995 p. 803-814, https://doi.org/10.1016/0584-8547(94)00160-w
Year1995
Alt SeriesGeological Survey of Canada, Contribution Series 30594
PublisherElsevier BV
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf
Subjectsgeochemistry; uranium; atomic absorption spectrometry; chemical analysis; analytical methods; uranium geochemistry; analyses; geochemical analyses; electrothermal vaporization; inductively coupled plasma mass spectrometry; graphite furnace atomic absorption spectrometry
Illustrationsanalyses
AbstractThe mechanism of vaporization and atomization of U in a graphite tube electrothermal vaporizer was studied using graphite furnace atomic absorption spectrometry (GFAAS) and electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS). Graphite furnace AAS studies indicate U atoms are formed at temperatures above 2400°C. Using ETV-ICP-MS, an appearance temperature of 1100°C was obtained indicating that some U vaporizes as U oxide. Although U carbides form at temperatures above 2000°C, ETV-ICP-MS studies show that they do not vaporize until 2600°C. In the temperature range between 2200°C and 2600°C, U atoms in GFAAS are likely formed by thermal dissociation of U oxide, whereas at higher temperatures, U atoms are formed via thermal dissociation of U carbide. The origin of U signal suppression in ETV-ICP-MS by NaCl was also investigated. At temperatures above 2000°C, signal suppression may be caused by the accelerated rate of formation of carbide species while at temperatures below 2000°C, the presence of NaCl may cause intercalation of the U in the graphite layers resulting in partial retention of U during the vaporization step. The use of 0.3% freon-23 (CHF3) mixed with the argon carrier gas was effective in preventing the intercalation of U in graphite and U carbide formation at 2700°C.
GEOSCAN ID204450

 
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