A Robust Procedure for High‐Precision Determination of Rare Earth Element Concentrations in Seawater

Abstract

This study reports a robust procedure that permits precise measurement of all fourteen naturally occurring rare earth element (REE) concentrations, present at ng kg−1 to sub ng kg−1 levels, in ~ 100 ml seawater. This procedure is simple and can be routinely applied to measure seawater REEs with relatively high sample throughput. The procedure involves addition of a 142Ce‐145Nd‐171Yb‐enriched spike mixture, iron co‐precipitation, REE purification with chromatographic separation and the use of a magnetic‐sector‐field ICP‐MS (Element 2) coupled with a desolvating sample introduction system (Aridus 1). Critical steps of the procedure, including co‐precipitation pH and matrix removal, have been optimised through a set of experiments described here. The accuracy of the new procedure was assessed against a gravimetric mixture of REEs, and the precision was demonstrated by repeated measurement of two well‐mixed natural seawaters. Repeated analyses of these seawater reference materials (RMs), using ~ 100 ml seawater for each aliquot, indicate precision of 3% (1s) for the REEs. Measured REE concentrations of two uncertified seawater RMs (CASS‐4 and NASS‐5) are consistent with published values, and REE concentrations of the GEOTRACES intercalibration samples show good agreement with those reported by other participant laboratories. REE concentrations for other intercalibration samples (SAFe and Arctic PS70) are also reported.

Rapid and precise analysis of rare earth elements in small volumes of seawater - Method and intercomparison

“…The detection limit of our analytical method for REEs, based on three times the standard deviation of the total procedural blanks (n=25) following Zheng et al (2015), ranged between 0.002 pmol/kg for Tm and 0.4 pmol/kg for Ce (Table 5), and was similar to those reported by Zheng et al (2015).…”

“…We used a standard solution with seawater-like relative REE concentrations in 2% HNO 3 (REE Coral Sea standard, Zheng et al, 2015, provided by Gideon Henderson, University of Oxford) as an external standard. We analyzed the standard both unspiked and spiked at each session at similar signal intensities as the pre-concentrated samples, except for Ce (~5 times higher in the standard).…”

“…However, we used a sample volume of 11-12 mL, while Zheng et al (2015) used 100 mL of seawater, indicating a major advancement in sample volume required for the analysis of REEs in seawater.…”

Fast Determination of Yttrium and Rare Earth Elements in Seawater by Inductively Coupled Plasma-Mass Spectrometry after Online Flow Injection Pretreatment

“…Thus YREEs must be separated and concentrated before detection. As pretreatment procedures, liquid-liquid extraction [ 5 , 15 , 16 , 17 ], co-precipitation [ 18 , 19 , 20 , 21 ], and solid-phase extraction [ 22 , 23 , 24 , 25 , 26 , 27 ] techniques have been utilized. Among these procedures, solid-phase extraction using chelating absorbents is becoming popular due to its wide selectivity of YREEs, low risk of contamination, freedom from toxic reagents and its simplicity for interfacing with ICP-MS to permit online determination when using flow injection (FI) as sample preconcentration systems.…”

Determination of rare earth elements in natural water samples – A review of sample separation, preconcentration and direct methodologies

“…Isotope ratios for several elements (Nd, Hf, U etc) were determined using a combination of high resolution ICP-MS and TIMS. A similar paper to discuss REE preconcentration in seawater using iron coprecipitation was presented by Zheng et al (143). Again, the precipitate was washed with dilute ammonia solution prior to separation of analytes from the matrix using chromatographic columns.…”