DETERMINATION OF TRACE LANTHANIDES AND YTTRIUM IN SEAWATER BY INDUCTIVELY COUPLED PLASMA MASS-SPECTROMETRY AFTER PRECONCENTRATION WITH SOLVENT-EXTRACTION AND BACK-EXTRACTION

A method for the analysis of sub parts per trillion levels of rare-earth elements (REEs) and yttrium (Y) In seawater after preconcentration with solvent extraction and back-extraction has been developed. Almost perfect extraction and back-extraction of all REE and Y were achieved by single extraction, and most of the matrix elements were removed during the extraction procedure. Even after 200-fold preconcentration, matrix problems by I CP-MS measurement were negligible. Contamination from reagents and water used during the pretreatment was below 1% of the concentration of REE and Y in seawater. The standard deviation obtained for triplicate separation of 100- and 1000-mL samples of the same seawater was better than 5% for all REE. The average precision of the measurement for all REE and Y after preconcentration of 1000 mL of raw seawater to 5 mL of final measurement solution was calculated to be less than 2.5 %. Since there is no standard seawater sample for REE and Y, in order to evaluate this novel technique, the analytical results obtained by this method were compared with those obtained by isotope dilution mass spectrometry coupled with Fe coprecipitation. The comparison indicated the good accuracy of the present method. Sample preparation and measurement could be carried out within 30 min for every sample. Two internal standard elements, In and Cd were used to check sample loss during the extraction and back-extraction procedures and to control the possible matrix effect and instrument fluctuation. © 1990 American Chemical Society. All rights reserved.