HR: 0800h
AN: V51B-0563    [Abstracts]
TI: Rapid U separation and its precise isotopic measurements using ICP-QMS
AU: Douville, E
EM: Eric.Douville@cea.fr
AF: Laboratoire des Science du Climat et de l'Environnement -CEA-CNRS-UVSQ, Batiment 12, Ave. de la Terrasse, Gif-sur-Yvette, 91198, France
AU: Salle, E
AF: Laboratoire des Science du Climat et de l'Environnement -CEA-CNRS-UVSQ, Batiment 12, Ave. de la Terrasse, Gif-sur-Yvette, 91198, France
AU: * Gourgiotis, A
EM: alkis.gourgiotis@lsce.cnrs-gif.fr
AF: Laboratoire des Science du Climat et de l'Environnement -CEA-CNRS-UVSQ, Batiment 12, Ave. de la Terrasse, Gif-sur-Yvette, 91198, France
AU: Ayrault, S
AF: Laboratoire des Science du Climat et de l'Environnement -CEA-CNRS-UVSQ, Batiment 12, Ave. de la Terrasse, Gif-sur-Yvette, 91198, France
AU: Frank, N
EM: Norbert.Frank@cea.fr
AF: Laboratoire des Science du Climat et de l'Environnement -CEA-CNRS-UVSQ, Batiment 12, Ave. de la Terrasse, Gif-sur-Yvette, 91198, France
AB: Here we present a largely simplified analytical separation technique for U from marin carbonates and sediments and U isotopic measurements obtained by inductively coupled plasma-source quadrupole mass spectrometer (ICP-QMS) Xseries II - Thermo Scientific. The separation of U is done from dissolved carbonates and sediments using a single ion exchange column packed with ~500 μg of UTEVA resin from EICHROM industries. The column is pre-cleaned and loaded by several rinses of MilliQ water and 3N HNO₃. Then earth alkali, transition metals and lanthanides are eluted quantitatively using 3N HNO₃. Pure Th and U solutions are then successively extracted from the column using 3N HCl and 1N HCl at ~100% yield. U solutions at ~25-50 ppb were injected into the ICP-QMS at conventional sample flow rates of approximately 1ml/minute, without particular injection systems such as a desolvator or μ - nebuliser. 30 scans with 180 sweeps and a dwell time of 50 ms per isotope were used to collect ²³³U, ²³⁴U, ²³⁵U and ²³⁶U on an electron multiplier. Baseline sensitivity was followed on mass 228 with <1cps at ~ 1000cps on mass 234. Then, mass discrimination was corrected using the ²³³U/²³⁶U spike of known isotopic ratio and HU1 reference solutions were used to test the reproducibility and to correct drifts using standard - sample bracketing. Overall ICPMS analyses yield a stunning reproducibility of <0.4 % at 2 σ, which is close to the one obtained by conventional TIMS instruments ~0.2-0.4 %. We have applied this technique to organic rich sediments and marine carbonate samples previously measured by TIMS and found a perfect agreement for both U concentration and its isotopic composition. This rapid and effective chemical purification and isotopic measurement of U allows to process more than 20 samples a day allowing to investigate large numbers of natural samples for weathering, tracer and geochronological studies.
DE: 1040 Radiogenic isotope geochemistry
DE: 1050 Marine geochemistry (4835, 4845, 4850)
DE: 1094 Instruments and techniques
DE: 1165 Sedimentary geochronology
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting