Determination of uranium in apatite minerals by inductively coupled plasma atomic emission spectrometry after solvent extraction and separation with 3-phenyl-4-benzoyl-5-isoxazolone into diisobutyl ketone

Solvent extraction with inductively coupled plasma atomic emission spectrometry (ICP-AES) was applied to the determination of uranium in apatite minerals. The combination of 3-phenyl-4-benzoyl-5-isoxazolone (HPBI), a highly acidic extracting reagent (pKa=1.23), and diisobutyl ketone (DIBK) make it possible to extract uranium from a very low pH region where uranium is separated from the interfering elements and the precipitation of calcium phosphate is avoided. Apatite minerals were treated with concentrated nitric acid. After removing a small quantity of insoluble residue, uranium was extracted with 0.06 M HPBI into DIBK at pH 0.3 in order to separate it from the interfering elements. Uranium was determined by ICP-AES and direct injection of the DIBK phase. A wavelength of 367.01 nm was selected which gave the highest intensity ratio, i.e., the emission intensity of uranium in DIBK to the background one, and the best detection limit (0.02 mg/l). The uranium content in the apatite was found to be (1.06±0.12)x10-2%