Combination of on-line preconcentration by di(2-ethylhexyl) phosphoric acid resin in the presence of complexing agent with microwave plasma-atomic emission spectrometry for the determination of rare earths

The adsorption of rare earths, lanthanum, cerium, neodymium, and yttrium by di(2-ethylhexyl) phosphoric acid (D2EHPA) resin in the presence of a complexing agent, EDTA, was investigated. Flow injection was selected as the injecting method. Various parameters, sample pH, sample loading time, sample flow rate, EDTA concentration, EDTA flow rate, eluent concentration, and eluent flow rate, were studied and optimized. Under the optimum conditions, the method allowed the determination of rare earths with detection limits of 1.09 μg/L (lanthanum), 3.31 μg/L (cerium), 2.05 μg/L (neodymium), and 1.25 μg/L (yttrium). High repeatabilities were obtained for all the four rare earths (RSD<5%). The proposed method was applied to the determination of the rare earths in water samples with a recovery range of 95.8%-103.3%.