Eichrom’s RE Resin is an extraction chromatographic material which consists of 1 M octyl(phenyl)-N,N-diisobutylcarbamoyl-methylphosphine oxide (abbreviated as CMPO)in tributyl phosphate(TBP) coated on an inert methacrylic polymeric support. The CMPO molecule is shown in Figure 1.

RE Resin is a favorable tool for the group separation of rare earth elements and has been used in conjunction with geological dating and radionuclide transport studies. Due to the high retention of yttrium on RE Resin it has also been applied to the purification of yttrium (Y90) used in cancer therapy.

The RE Resin is analogous to Eichrom’s TRU Resin. Both are composed of the same extractant system (CMPO/TBP), but the concentration of CMPO is higher in the RE Resin. This increases its affinity for rare earth elements and yttrium out of acidic aqueous solutions. Figure 2 and 3 compare the uptake of selected lanthanide elements on the two resins on a log scale. It can be seen that the uptake of these elements is typically twice as high on RE Resin as on TRU Resin.

Figures 4 and 5 show plots of the distribution factor, k’, vs. nitric acid for all of the lanthanide elements, as reported by Huff and Huff. Note that for all the lanthanide elements, k’ increases with increasing nitric acid up to 4M. At higher acid concentrations, k’ increases for the heavier lanthanides, but falls off for the lighter lanthanides.

Figures 2-5 were calculated from weight distribution data generated by Huff & Huff (HD193). Eichrom’s commercial product is manufactured to established quality specifications. Please refer to our product specificationsfor details.

Esser, et. al. developed a method for measuring rare earth elements in environmental water samples. They observed breakthrough of the heavier lanthanides during load (15 FCV) and rinse (25 FCV) steps when the load/strip solutions were 2 and 4N nitric acid. When 6N nitric acid was used, no breakthrough of any lanthanides was observed. This demonstrates the acid dependency of the heavy lanthanides shown in Figure 5.

Experiments conducted by Huff & Huff show that only Zr, Th and U are retained on RE Resin over the whole nitric acid range. These researchers did not evaluate the retention of other actinide elements, but, by extrapolation from known data on TRU Resin, it is expected that all the actinides would show strong retention at 1M and higher nitric acid.

Dietz and Horwitz (1992) investigated the use of RE Resin in the production of 90Y for radiopharmaceutical use. In this application, the radiation stability of the resin is quite important because of the high activities loaded onto the column. RE Resin was exposed to increasing doses of absorbed radiation and the k’ for americium from low acid (0.05M HNO3) and high acid (2M HNO3) concentrations was measured. The data presented in Table 1 indicates that the RE Resin was unaffected by the radiation exposure.

Table 2 shows the elution behavior of various elements on the RE Resin. Fractions 1-6 correspond to 1.8 FCV each, fractions 7 and 8 to 3.6 FCV each, and fractions 9 and 10 to 9.0 FCV each. This data indicates that elements which are commonly present in environmental samples can be readily separated from lanthanide elements using RE Resin.

Decontamination factors for the elements shown in Table 2 were calculated by dividing the initial concentration of that element by the concentration found in fraction number 5. These are presented in Table 3. Numbers presented as “>” were calculated using the detection limit in the denominator. It can be seen, that generally, these decontamination factors are quite large.

The work by Dietz & Horwitz, reported above, dealt with the separation of 90Y from it’s parent, 90Sr. The overall procedure they presented employed multiple Sr Resin separations followed by a final RE Resin separation. Overall they were able to reduce the level of 90Sr by a factor of >4.5 x 108. Please contact Eichrom if you want to receive additional details on this work.

RE Resin is manufactured in three particle sizes (20-50µ 50-100µ, and 100-150µ) 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.