Sorption Characteristics and Chromatographic Separation of 90Y3+ from 90Sr2+ from Aqueous Media by Chelex-100 (Anion Ion Exchange) Packed Column

Abstract

There is growing demand for separation of ⁹⁰Y carrier free from ⁹⁰Sr coexisting to produce high purity ⁹⁰Y essential for radiopharmaceutical uses. Thus, in this context the sorption profiles of Y³⁺ and Sr²⁺ from aqueous solutions containing diethylenetriaminepenta acetic acid (DTPA), ethylenediaminetetra-acetic acid (EDTA), acetic acid, citric acid, or NaCl onto Chelex-100 (anion ion exchange) solid sorbent were critically studied for developing an efficient and low-cost methodology for selective separation of Y³⁺ from Sr²⁺ ions (1.0 × 10^-5 M). Batch experiments displayed relative chemical extraction percentage (98 ± 5.4%) of Y³⁺ from aqueous acetic acid solution onto Chelex-100 (anion ion exchanger), whereas Sr²⁺ species showed no sorption. Hence, a selective separation of Y³⁺ from its parent ⁹⁰Sr²⁺ has been established based upon percolation of the aqueous solution of Y³⁺ and Sr²⁺ ions containing acetic acid at pH 1-2 through Chelex-100 sorbent packed column at a 2 mL min^-1 flow rate. Y³⁺ species were retained quantitatively while Sr²⁺ ions were not sorbed and passed through the sorbent packed column without extraction. The sorbed Y³⁺ species were then recovered from the sorbent packed column with HNO₃ (1.0 M) at a 1.0 mL min^-1 flow rate. A dual extraction mechanism comprising absorption associated to "weak-base anion exchanger" and "solvent extraction" of Y³⁺ as (YCl₆)^3- and an extra part for "surface adsorption" of Y³⁺ by the sorbent is proposed. The established method was validated by measuring the radiochemical (99.2 ± 2 1%), radionuclide purity and retardation factor (R_f = 10.0 ± 0.1 cm) of ⁹⁰Y³⁺ recovered in the eluate. Ultimately, the sorbent packed column also presented high stability for reusing 2-3 cycles without drop in its efficiency (±5%) towards Y³⁺ uptake and relative chemical recovery. A proposed flow sheet describing the analytical procedures for the separation of ⁹⁰Y³⁺ from ⁹⁰Sr²⁺ using chelating Chelex 100 (anion exchange) packed column is also included.