The combined application of both Nd and Sr isotope ratios in mid-ocean ridge and ocean island basalts can be used as probes into the earth's interior for studying the mantle, the nature and scale of its heterogeneities and its dynamics. Accurate determination of the isotopic composition of neodymium for geochronological work using mass spectrometry requires the separation of the element from other rare earth elements (REE) using chromatography as a tool.
The complexing agent di(2-ethylhexyl) phosphoric acid (HDEHP) has been fixed on porous styrene divinylbenzene copolymer (Bio-beads S-X8 beads), and this mixture was used as column support material for chromatographic elution of the REE. Optimal conditions of Nd separation from other REE using HDEHP coated onto Bio-beads S-X8 beads as the column support have been established.
The application of this method in rock samples is focused on the efficient low-blank Nd separation to avoid unwanted isobaric interference during mass spectrometry.
This column support material can be conveniently prepared and shows a reproducible behavior and sharp elution peaks are obtained at room temperature (23±2 °C). Columns used in this work, coated with 10% of HDEHP (relative to the weight of beads) were perfectly stable, and can be regenerated and re-used for about 30 runs with only a slight loss of exchange capacity.
Several performance parameters of HDEHP-beads column were also investigated. The effect of concentrations of HCI in the 10% w/w HDEHP-beads column for the four REE, La, Ce, Pr and Nd has been studied. The optimal HC1 concentration for Nd was found to be 0.26M. At room temperature (23 ± 2 °C), the optimal flow rate was 0.84 ml cm-2min-1.
The advantages of the HDEHP-beads column are: the most appropriate conditions for the separation of adjacent lanthanide pairs can be established; the procedure is not time-consuming and can be satisfactorily carried out at room temperature; the column support has a large surface area per unit volume, a long life time and no channelling problem; and the high stability and the good regeneration of the column, without losing extractant quality, yield a good separation for the four lanthanides La, Ce, Pr and Nd. [...]
