UTEVA Resin has been applied to a variety of analytical challenges. These include uranium measurements in environmental samples, sample preparation of high uranium content samples prior to analysis for other elements, the sequential determination of uranium, plutonium, and americium, the measurement of actinides in urine, and the measurement of actinides in high level waste.
The extractant in the UTEVA Resin, diamyl, amylphosphonate (DAAP, see Figure 1), forms nitrato complexes with the actinide elements. The formation of these complexes is driven by the concentration of nitrate in the sample solution. Therefore, the uptake of the actinides increases with increasing nitric acid concentration. Figure 2 is a plot of the k'(a measure of uptake corresponding to the number of free column volumes to peak maximum) vs. nitric acid concentration.
It can be seen that the uptake from nitric acid is very similar for each of the tetravalent actinides and uranium. All have strong retention (k’>100) above 5M nitric acid. Note that Am is not retained at any nitric acid concentration. This fact is important in developing analytical separation schemes. Plutonium can be reduced to Pu(III) with ferrous sulfamate. At this valence state, it behaves the same as Am(III).
Figure 3 is a similar graph that shows the effect of HCl on the retention of tetravalent neptunium, thorium, and hexavalent uranium on UTEVA Resin. The large difference in k’ for uranium and thorium in the range of 4-6M HCl allows for the selective elution of Th from the resin after both Th and uranium have been loaded.
Figure 2 implies that uranium can be stripped efficiently from the UTEVA Resin with a relatively small volume of very dilute nitric acid (e.g., 0.01-0.05M). In practice, however, it appears that HCl is more efficient in stripping uranium and it is recommended that, where possible, HCl be used in place of nitric acid. Concentrations up to 1M HCl have been shown to quantitatively elute uranium. 15mL is a sufficient volume for a 2mL pre-packed column.
Horwitz, et al. reported the data in Figures 2 and 3 from studies performed with experimental batches of UTEVA Resin. Eichrom’s commercial product conforms to established specifications that ensure proper performance of Eichrom issued methods. Please refer to our product specificationsfor details.
As in most analytical situations, the presence of significant concentrations of matrix elements can affect the proper operation of methods based on UTEVA Resin. Figures 4 and 5 show the effect of certain polyatomic anions on the retention of neptunium and uranium, respectively, from 2M nitric acid. It should be noted that the effect on tetravalent neptunium is more significant than the affect on uranium. It has been seen in practice that thorium is affected similarly to neptunium by these anions.
Because phosphate occurs quite commonly in a variety of biological and environmental samples, its effect is most relevant. Fortunately the addition of aluminum to the sample matrix can significantly reduce this issue. Phosphate anion readily complexes tetravalent actinides. This phosphato complex is not extracted by the DAAP. Added aluminum can effectively tie up the phosphate preventing its interference with neptunium (or thorium) uptake by the resin. In some methods, as much as 1M Al(NO3)3 might be added to counteract the effects of phosphate.
The theoretical maximum loading capacity of UTEVA Resin for uranium is approximately 37 mg/mL of resin bed. In practice, it is not recommended to exceed 20% of this amount, or 7.5mg per mL of resin. This corresponds to a working capacity for uranium of 15 mg per 2mL pre-packed column. The bed density of UTEVA Resin is 0.39 g/mL.
UTEVA Resin is manufactured in three particle sizes (20-50m, 50-100m, and 100-150m) and is sold in bottles or, ready to use, in prepackaged columns (for gravity flow) and cartridges (for vacuum assisted flow.) Click here for part numbers and descriptions.
Source: Horwitz, E.P., et al, Separation and preconcentration of uranium from acidic media by extraction chromatography, Analytica Chimica Acta, Vol.266, pp. 25-37(1992) (HP392)