A 232Th and 238U sample was separated using UTEVA resin.
The separation procedure includes the following steps:
· Transfer the solution prepared in the previous stage to a glass beaker and gently evaporate to incipient dryness on a hot plate at 1300C
· Re-dissolve in 5 mL of 9M HCl and load on an UTEVA column, pre-conditioned with 10mL of 9M HCl
· Rinse with 20 mL of 9M HCl to remove the matrix
· Elute the Th(IV) fraction with 20 mL of 5M HCl in pre-weighted 50 mL plastic test-tube.
· Elute the U(VI)) fraction with 20 mL of 1M HCl in pre-weighted 50 mL plastic test-tube.
At each stage of the separation, the weight of the empty and full vial was recorded, and then a weighed 1 mL aliquot taken for ICP-MS measurement.
Dilution factor correction for ICP-MS samples 10
Load solution ( 24.75 g )
Thorium fraction ( 10.43 g)
Uranium fraction ( 14.36 g)
Aliquot masses for ICP-MS
Load solution (1.095 g)
Load solution collected from UTEVA column (1.16 g)
Thorium fraction (1.09 g)
Uranium fraction (1.02 g)
ICP-MS CPS attached
how to calculate the recovery of each fraction relative to the starting solution? i have no idea
Mr. Alharbi,
The deffinition of 'recovery' togenther with the equation can be found in books devoted to chemometrics.
Dear Moha
I fear your data are inconclusive at this stage. To calculate the recovery you would formally need to determine the total masses of U and Th loaded and their total masses post column. To do so you would need to calibrate the sensitivity of the instrument for each isotope and know the masses of all solutions in all dilution steps. If you assume that the sensitivity of the ICPMS is identical for all solutions measured (which I wouldn't assume a priori and add at least one internal standard to monitor that) you may consider the ratios of the net cps directly proportional to the concentration ratios in the measured solutions. By considering the dilution factors you can then get an estimate of the isotopes' mass ratios relative to the starting solution. I am however not sure what dilution factors you used. From the data you provide it is not clear if the load solution (24.75 g) is the mass of sample before evaporation or the mass of the solution loaded on the column (which should be about 5 g only).
ICP-MS is one of the best technique for trace element analysis, but we should be assured that the conditions during the instrument calibration and sample analysis is same. The counts recorded in the sample is calculated with the help of calibration graph. In your work you are trying to separate Th from U matrix, but you are not mentioning the initial amount taken. The analyte may be contaminated during the separation procedure, therefore, a blank correction is essential. If total dissolved solid (TDS) is >2% in the samples analyzed by ICP-MS then chances of error will be high, so that dilute the sample to bring TDS below 2%. You can repeat your work with synthetic sample of (U and Th) or using a certified reference materials to study the recovery using column. Solutions should be in 1-2% HNO3 or HCl to avoid hydrolysis.
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