Determination of Rare Earth Elements in Pore Water Samples of Marine Sediments Using an Offline Preconcentration Method.

Abstract

The concentrations of dissolved yttrium and rare earth elements (REY) in sediment pore water provide important geochemical information. However, due to the low REY concentration, complex matrix, and limited sample volume (often only a few milliliters), analysis of the REY in pore water often is highly challenging. In this study, a method was established to determine the dissolved REY in pore water of marine sediments using an offline preconcentration step with the ethylenediaminetriacetate chelating resin, followed by inductively coupled plasma-mass spectrometry. In addition, using a commercially available automated trace-element preconcentration system, the preconcentration step can be fully automated, saving labor and providing a better control of the final elution volume. The experimental conditions (pH, elution volume, elution acid concentration, and organic complexation effect) were assessed, and the optimal conditions were chosen. In particular, the organic complexation effect was found to be negligible. The procedure blank and limit of detection were satisfactory for studying REY in pore water of marine sediments, and the method also yielded satisfactory recoveries for the REY elements (83-110%). The method was then applied to analyze the dissolved REY concentrations of pore water samples collected in a sediment core (~ 30cm) in the central Indian Ocean. The vertical distribution, dissolved REY concentration, and the average Post Archean Australian Shale-normalized pattern of the REY showed similarities to the previously published pore water REY data. This method provides an accurate yet facile approach for the analysis of all 15 REY in marine pore water samples using the sample volume of only ~ 5mL.