Pre-concentration 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 other 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, neodymium, samarium and yttrium mixtures and subsequent determination by energy dispersive X-ray fluorescence spectrometry is described. The pre-concentration procedure, which involves the use of silica modified with 1-(2-pyridylazo)-2-naphthol, permits complete recovery of the rare earths and significant sensitivity enhancement in comparison with direct determination in the aqueous phase. Determinations in quaternary mixtures show typical precisions and accuracies of 3% and 5%, respectively.