I'm an old time radiochemist. My first choice is digestion, separation (Eichrome cartridge) and alpha spectroscopy. If you have that equipment it is good, if you have the ICP-MS it also works.

Mr. Costa,

By ICP-MS (total concentration).

Hi there,

Old methods are still valid.

Elsevier - Chemosphere

Volume 63, Issue 7, May 2006, Pages 1165-1169

Spectrophotometric determination of uranium with arsenazo-III in perchloric acid

Muhammad HaleemKhana PeterWarwickb NickEvansbShow morehttps://doi.org/10.1016/j.chemosphere.2005.09.060

Abstract

A short, sensitive and reliable spectrophotometric method, which has advantages over all known “wet chemistry” methods for uranium determination with regard to tolerance to common interferences, has been developed for the determination of uranium. Selectivity, molar absorptivity and the determination range of uranium have been enhanced by using 0.07% arsenazo-III as a chromogenic reagent. The use of 3 mol dm−3 perchloric acid as a medium of determination was found to be excellent in terms of good solvent compatibility on dilution, destruction of organic contamination and simplicity of operation. The uranium–arsenazo-III complex formed instantly, and was found to be stable for more than 3 weeks with constant absorbance. Beer’s law was obeyed up to a uranium concentration of 16 μg g−1, with a molar absorptivity at 651 nm of 1.45 × 105 mol−1 dm3 cm −1 at 24 ± 2 °C. Only phosphate and citrate at 70-fold excess over uranium interfere seriously, whereas other anions studied could be tolerated up to a 70-fold excess over uranium. Of the cations studied, only Mn(II), Co(II), Ni(II), Cu(II) and Cr(III) decreased the normal absorbance of the complex. Iron(III), Ce(III) and Y(III) enhanced the absorbance. Other cations studied did not affect the absorbance up to a 50-fold excess. The accuracy was checked by determining uranium from standard solutions in the range 10–50 μg g−1. It was found to be accurate with a 96.0–98.6.% recovery rate. The method has been successfully applied to standard reference materials and ore samples at μg g−1 levels.

Dear Ivanova,

How prepare sample to do it in the ICP-MS?

DEPENDS ON THE SAMPLE!

Jorge,

To oil sample

You can use ICP-MS or XRF.

regards,

G

I'm an old time radiochemist. My first choice is digestion, separation (Eichrome cartridge) and alpha spectroscopy. If you have that equipment it is good, if you have the ICP-MS it also works.

Thanks for all answers!

I am realizing that the methods is basicly ICP-MS and alpha spectroscopy.

ICP-MS is easier to me obtain access in the lab. How to prepare crude oil or machine oil sample?

Mr. Costa,

For environmental oil samples and/or industrial oils the ISOs are shown, here:

https://www.iso.org/files/live/sites/isoorg/files/news/magazine/ISOupdate/EN/2018/ISOupdate_February_2018.pdf

For foodstuff oil sample: ISO 17294-2 2005

The protocols are for ICP-MS. For other methods there are other ISOs.

Gilberto,

Have got your answer?

Yes.

Thank you all

Dear Dr. Costa,

i use tha Alpha spectroscopy because is possible measure all Uranium Radionculides, U-238, U-234 and U-235. Normally after tracers adding is possible sparate Uranium form other radionuclides by Ion-exchange resin, and in second step with the effluents collected by first resin, you can separate the Thorium by Radium and other elents using another ion-exchange resin.

By the way, If correct, i think in ICP-MS U-234 determination is not easy, or possible...but some collegues could confirm it, but is a good method, with high sensibility; the MDA, Minimum Detectable Acitivity, in XRF in my opinioni is very high...and for my goals isn't good.

The good method to measure Uranium and Thorium is fundamental to obtain all information about your sample,in this specific case the equilibrium between 238/234.

At this link you can start to study different method to measure Uranium and Thorium in different kind o sample:

https://www.epa.gov/sites/production/files/2015-06/documents/epa-emsl-33.pdf

The other key point, using the Alpha spectrometry, is the perfetc dissolution of sample or Uranium extraction before separation/purification steps.

Best Regards

Mattia

What kind of samples

XRF

The hyphanated techniques are the best for examples using SPE-ICP or ICP-MS

In my opinion, if our collegue would measure the Uranium, 238, 234 and 235, obtaining the separate concentration, like as about Thoriun (232, 228), the best way is theb alpha spectrometry, because this technique is able to measure all the radionuclides mantined above with very low MDA, Minimum Detectable Acitivity. Maybe the ICP-MS is not able to measure the U-234 with low MDA? Is correct?

Thanks