Determination of uranium and thorium in apatite minerals by inductively coupled plasma atomic emission spectrometry with solvent extraction separation into diisobutyl ketone

Determination of the actinide elements (uranium and thorium) in apatite minerals has been examined by inductively coupled plasma atomic emission spectrometry (ICP-AES) with solvent extraction separation. The spectral interference by calcium in the apatite and the negative interference by the macro-component (calcium phosphate) occurred simultaneously for uranium and thorium. Therefore, after apatite mineral was treated with hot concentrated nitric acid, uranium and thorium were separated from calcium phosphate by the solvent extraction method. 1-Phenyl-3-methyl-4-trifluoroacetyl-5-pyrazolone (HPMTFP, pK(a)=2.56) was used as an extraction reagent in the present study. Diisobutyl ketone was selected as the extraction organic solvent. Uranium and thorium were quantitatively extracted over pH 2, and could be separated from the apatite composites. The organic phase was injected directly into the ICP-AES spectrometer. The uranium and thorium contents in apatite minerals from Florida, USA, were found to be 103+/-2.2 and 8.84+/-0.19 ppm. These results were quite comparable with those measured with ICP-mass spectrometry (ICP-RIS). (C) 2000 Elsevier Science B.V. All rights reserved.