PRECONCENTRATION OF RARE-EARTHS USING SILICA-GEL LOADED WITH 1-(2-PYRIDYLAZO)-2-NAPHTHOL (PAN) AND DETERMINATION BY ENERGY-DISPERSIVE X-RAY-FLUORESCENCE

The determination of a single rare earth element in a mixture with oth er species of this family is a very challenging problem in analytical chemistry due to the close similarity of their chemical properties. In this work, a liquid-solid extraction procedure for praseodymium, neod ymium, samarium and yttrium mixtures and subsequent determination by e nergy dispersive X-ray fluorescence spectrometry is described. The pre -concentration procedure, which involves the use of silica modified wi th 1-(2-pyridyrazo)-2-naphthol, permits complete recovery of the ran e arths and significant sensitivity enhancement in comparison with direc t determination in the aqueous phase. Determinations in quaternary mix tures show typical precisions and accuracies of 3% and 5%, respectivel y. (C) 1998 Elsevier Science B.V. All rights reserved.