A straightforward separation scheme for concomitant Lu-Hf and Sm-Nd isotope ratio and isotope dilution analysis

A new method is described for the concomitant use of the Lu-Hf and Sm-Nd radiogenic isotope systems on the same rock digest. After total spiking with two mixed 176Lu-179Hf and 149Sm-150Nd enriched tracers, the sample is decomposed by fusion with a LiBO2 flux in an induction furnace. Hf is first separated from all matrix elements using U-TEVA Spec extraction chromatography material in 3 M HNO3 medium, and obtained in a single step ready for isotope ratio measurements using multiple collector ICP-MS [B. Le Fevre, C. Pin, Anal. Chem. 73 (2001) 2453]. The rare earth elements (REE) are then separated as a group from the same sample solution by conventional cation-exchange in nitric acid-oxalic acid medium. After evaporation of the REE fraction, Nd, Sm, and Lu are isolated by extraction chromatography using two tandem columns filled with RE Spec and Ln Spec extraction chromatographic materials, respectively. This separation scheme provides fractions of the analytes with excellent recoveries (>90%) and purity, suitable for thermal ionization mass spectrometry, with satisfactory blanks. The potential and present limitations of this method, are exemplified by repeat analyses of several international standard reference materials