Analysis of rare earth elements in seawater by inductively coupled plasma mass spectrometry after pre-concentration using TSK™-HD-MW-CNTs (highly dispersive multi-walled carbon nanotubes)

This study aimed to identify easy-to-use multi-walled carbon nanotubes (MW-CNTs) having a high capacity to adsorb metals and thereby expand the usability of these materials as a solid-phase adsorbent for the analysis of trace metals in seawater. High-dispersion-type MW-CNTs had the highest metal binding capacity (70.8 +/- 5.1 mg/g for La) after a strong acid oxidation procedure, possibly because the high dispersibility resulted in a more complete reaction than with highly crystalline types. Because the high-dispersion-type MW-CNTs leaked from a conventional column, they were attached to polymer beads (TSK (TM)) (pore diameter about 20 pm). Flow rate, pH, and volume of the seawater sample, as well as eluent type and volume, were optimized to obtain 0.01-0.16 pg/mL detection limits for rare earth elements (REEs). In addition, normalized patterns for samples collected from the East Sea showed characteristic features of REEs in seawater, i.e., a negative Ce anomaly, low atomic number REE (LREE) depletion, and high atomic number REE (HREE) enrichment. (C) 2012 Elsevier B.V. All rights reserved.