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Appendix II: Laboratory protocols and MC-ICP-MS
function
II-a. Laboratory protocol for the separation of U and Th for
measurement with the MC-ICP-MS
A chromatographic separation of Uranium and Thorium
Preparations:
• Weighing ~0.3g of material with a uranium concentration of about 0.2-
0.3 ppm.
• Dissolving the samples with 7N of HNO 3 acid in centrifugal test tubes.
• The remaining insoluble material is separated with centrifuge and
transported to a separate Teflon container.
• A spike ( 236 U- 229 Th) is added and measured and then the sample is left
until equilibrium is reached.
• The solution is evaporated and then another 7N of NHO 3 is added and
a clear solution is received.
• The insoluble material is dissolved with 5ml of a mixture of
concentrated HF and HNO 3 .
• The detritic, insoluble matter is added to the solution.
• The solution is evaporated and more 7N HNO 3 is added
Chromatographic separation:
• Resin (Ag 1 x 800 200-400 mesh) is added to colons which are then
washed twice with 6N of HCl and three times with distilled water (TD
H 2 O).
• Preconditioning the colons to the solution by washing them with
HNO 3 .
• Adding the samples to the colons and washing them with 7N HNO 3
three times.
• Preconditioning the colons to thorium collection using 6N HCl.
• Adding 3.5ml of 6N HCl to the colons and collecting the thorium in
Teflon containers.
• Preconditioning the colons to uranium collection using 1N HBr.
• Adding 3.5ml of 1N HBr to the colons and collecting the uranium in
Teflon containers.
• Evaporation of the separated solutions until they are completely dry.
• Adding 2-3ml of 0.1N HNO 3 to the uranium in the Teflon containers
and moving it to centrifugal test tubes.
• Adding 5ml 0.1N HNO 3 to the thorium in the Teflon containers and
moving it to centrifugal test tubes.
• Measuring the concentration of uranium in the samples from the
solution with the ICP-MS.
• Diluting the samples with a high concentration (more than the standard
50ppb).
• Adding 25µl of standard 112a U NBL, in which the 234 U/ 238 U is
known, to the thorium test tubes.