Determination of Nd isotopes in water: A chemical separation technique for extracting Nd from seawater using a chelating resin

A new preconcentration technique for the deter-mination of the concentration and isotopic composition of neodymium in aqueous samples is presented. The method uses a resin, Nobias PA1 from Hitachi High-Technologies, which has a hydrophilic methacrylate polymer backbone where the functional groups ethylenediaminetriacetic and iminodiacetic acids are immobilized. The function of the resin has been tested by preconcentrating 110−350 pmol of Nd from test solutions as well as from natural brackish water and seawater samples with different salinities and Nd concentrations. Samples were loaded onto the resin after the pH was adjusted, and the Nd fraction was eluted using 3 M HNO3. The method shows yields of about 90% or higher at pH 6 when the samples were buffered using ammonium acetate. Without the addition of buffer the yield decreased to below 80%. The isotopic composition of Nd in samples preconcentrated using Nobias PA1 agree within error with published data or data obtained by other methods. The total blank, including contributions from preconcentration, separation, and mass spectrometry, is estimated to be 0.2−0.4 pmol (30−60 pg) of Nd. The described preconcentration method, which can be used in the field, is easy, fast (about 8 h for a 3.6 kg sample), and reliable for preconcentration of Nd from a seawater matrix.