Separation And Determination Of Ultratrace Rhenium Quantities In Molybdenum Matrix

The production of very pure molybdenum, free of Re even at ultratrace levels, is extremely important in meeting target purity specifications during the production of Mo-99 for medical applications. Here we propose two methods for separating ultratrace levels of Re from a bulk Mo matrix using either solvent extraction or extraction chromatography, combined with inductively coupled plasma quadrupole mass spectrometry (ICP-MS) detection. Re is extracted (D > 70) from solutions in sulfuric acid as a complex with tri-n-butyl phosphate. Scrubbing and washing steps result in total decontamination factors for Mo up to 1,700 for solvent extraction and 3,500 for extraction chromatography. Re is stripped into a 3 M NH4OH matrix and analyzed by ICP-MS. Detection (L-D ) and quantification (L-Q ) limits were optimized by matrix-matching to allow detection of Re in strip solutions at levels of L-D = 0.1 ng Re/g-Mo and L-Q = 0.3 ng Re/g-Mo in Mo powder samples. By employing these two extraction methods, excellent recoveries of Re from bulk Mo are achieved, and the L-Q is improved by a factor of 5 x 10(4).