State of the art in the determination of trace elements in seawater: a worldwide proficiency test.

Pieter Dehouck,Beatriz De La Calle,Fernando Cordeiro,James Snell

doi:10.1007/s00216-016-9390-6

Pieter Dehouck, Beatriz De La Calle + Show 2 more

Open Access

https://doi.org/10.1007/s00216-016-9390-6

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Abstract

This manuscript presents the results of the International Measurement Evaluation Programme 40 (IMEP-40) study, a proficiency test (PT) which was organised to assess the worldwide performance of laboratories for the determination of trace elements in seawater. This PT supports the implementation of the European Union Water Framework Directive 2000/60/EC, which aims at achieving a long-term high level protection of the aquatic environment, covering lakes, ground water and coastal waters. Forty-six participants reported results. The test item was seawater containing the trace elements As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Se and Zn. The trace elements in the test item were present in very low concentrations to mimic natural levels. The results of the participants were rated with z and zeta (ζ) scores in accordance with ISO 13528 and ISO 17043. The standard deviation for proficiency assessment, widehat{upsigma} , was set at 25 % of the respective assigned values for the 12 measured elements based on previous experience with similar PTs. The low levels of the trace elements combined with the high salt concentration of the seawater made the measurements challenging. Many laboratories were unable to detect or quantify the elements and reported “lower than X” values. The percentage of satisfactory performances (expressed as z scores) ranged from 41 % (Cr, Fe) to 86 % (Mo). The PT study showed that the use of proper standard methods, like ISO 17294-2, and sensitive techniques, like inductively coupled plasma mass spectrometry (ICP-MS), contributed to performing well in this PT round.

Highlights

The monitoring of trace elements in seawater is relevant for the implementation of the Directive 2000/60/EC (Water Framework Directive (WFD)), which aims at achieving a long-term high level protection from chemical pollution of the aquatic environment, covering lakes, ground water and coastal waters [1]
Regarding the trace elements investigated in this proficiency test study, maximum allowable concentrations in seawater are set for Cd (0.45 μg L−1), Pb (14 μg L−1) and Ni (34 μg L−1) [2]
One laboratory reported results in micrograms per kilogram. These results were converted into micrograms per litre using a density of 1.02352 g mL−1 which was determined for this candidate Certified Reference Material (CRM)

Summary

Introduction

The monitoring of trace elements in seawater is relevant for the implementation of the Directive 2000/60/EC (Water Framework Directive (WFD)), which aims at achieving a long-term high level protection from chemical pollution of the aquatic environment, covering lakes, ground water and coastal waters [1]. The levels of a number of trace elements present in this study (As, Cd, Cr, Cu, Ni, Pb, Zn) are limited by Directive 2006/113/EC on the quality required of shellfish waters [3]. This directive applies to coastal and brackish waters that need protection or improvement in order to support shellfish (bivalve and gastropod molluscs) life and growth and contribute to the high quality of shellfish products edible by man. Recent research has revealed the important role of trace elements in controlling marine biogeochemical processes [5]

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