Selective separation and determination of uranium in calcite and gypsum after EDTA-mediated sample dissolution and cation-exchange

Abstract

The present paper describes a relatively simple, effective, very selective and economic method for the determination of uranium in calcite and (phospho)gypsum samples. The analysis is performed by alpha-spectroscopy after dissolution of the samples in Na2-EDTA solution, uranium separation by cation-exchange and its electrodeposition on stainless steel discs. The method has been applied to 1 g limestone, chalk and (phospho)gypsum samples, resulting in high-quality spectra for measurement times between 6 and 72 h. The separation efficiency of the method is (75 ± 10)% and (65 ± 20)%, and the detection limit 0.2 mBq g−1 (4 mg kg−1) and 0.3 mBq g−1 (6 mg kg−1), for the gypsum and calcite samples, respectively. Moreover, the use of tracer solution (232U) allows method evaluation and accurate uranium determinations.