Environmental Chemistry Environmental Chemistry Society
Environmental problems - Chemical approaches
RESEARCH FRONT

Lead electrochemical speciation analysis in seawater media by using AGNES and SSCP techniques

Margarita Díaz-de-Alba A , M. Dolores Galindo-Riaño A C and José Paulo Pinheiro B

A Department of Analytical Chemistry, Faculty of Sciences, University of Cadiz, Campus Río S. Pedro, E-11510 Puerto Real, Cadiz, Spain.

B IBB/CBME, Department of Chemistry and Pharmacy, Faculty of Science and Technology, University of Algarve, Campus Gambelas, PT-8005-139 Faro, Portugal.

C Corresponding author. Email: dolores.galindo@uca.es

Environmental Chemistry 11(2) 137-149 http://dx.doi.org/10.1071/EN13154
Submitted: 20 August 2013  Accepted: 17 January 2014   Published: 9 April 2014

Environmental context. Metal contamination of seawater can present severe environmental problems owing to the high toxicity of metals and their persistence in the environment. This study explores the possibility of analysing lead in seawater media using two recently developed electrochemical methods. The methods are shown to be very useful tools to monitor the behaviour and fate of lead and other metals in seawater.

Abstract. The speciation of PbII in synthetic and real seawater is studied by absence of gradients and Nernstian equilibrium stripping (AGNES) and stripping chronopotentiometry at scanned deposition potential (SSCP). The usefulness of the combination of both techniques in the same electrochemical cell for trace metal speciation analysis is assessed at different pH values (2.7, 5.0, 6.0, 7.0 and 8.6). The AGNES (free metal ion concentrations) and SSCP (stability constants) results for synthetic seawater agree reasonably with each other and with the theoretical predictions of the software Visual MINTEQ 3.0. This is also true for real seawater media below pH 7.0. Because of the influence of natural organic matter (2.01 mg L–1 total organic carbon) in the real seawater at pH 7.0 and 8.6 the SSCP signal showed that the PbII complexes became less labile and were formed by chemically heterogeneous ligands. At these pH values, free metal concentrations determined by AGNES agreed with concentrations predicted by Visual MINTEQ using a generic fulvic acid concentration.

Additional keywords: absence of gradients and Nernstian equilibrium stripping, stripping chronopotentiometry at scanned deposition potential, Visual MINTEQ.


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