DETERMINATION OF TRACE-METALS IN URANIUM OXIDE BY INDUCTIVELY COUPLED PLASMA MASS-SPECTROMETRY COMBINED WITH ONLINE SOLVENT-EXTRACTION

An on-line solvent extraction technique for the determination of trace elements in uranium by inductively coupled plasma mass spectrometry is described. An aqueous solution containing uranium (2% m/v) in 1 mol dm-3 nitric acid and an organic solvent that can effectively extract uranium, viz., trioctylphosphine oxide in cyclohexane (0.2 mol dm-3), are pumped alternately through a poly(tetrafluoroethylene) (PTFE) tube where they mix thoroughly. The organic phase containing the extracted uranium is removed on-line by allowing the solution to pass through a microporous PTFE tube which, being hydrophobic, selectively allows the organic phase to permeate through its walls. This technique facilitates rapid and sensitive determination of trace elements in uranium with detection levels in the range 1-45 ppb for La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Yb, Ag, Ba, Cd, Co, Cr, Cu, In, Li, Mn, Ni, Pb, Sr, Ti, V and Y, 0.1 ppm for Al and 0.5 ppm for Fe.