Electrochemical sensors and devices for heavy metals assay in water: the French groups' contribution

Abstract

A great challenge in the area of heavy metal trace detection is the development of electrochemical techniques and devices which are user-friendly, robust, selective, with low detection limits and allowing fast analyses. This review presents the major contribution of the French scientific academic community in the field of electrochemical sensors and electroanalytical methods within the last 20 years. From the well-known polarography to the up-to-date generation of functionalized interfaces, the different strategies dedicated to analytical performances improvement are exposed: stripping voltammetry, solid mercury-free electrode, ion selective sensor, carbon based materials, chemically modified electrodes, nano-structured surfaces. The paper particularly emphasizes their advantages and limits face to the last Water Frame Directive devoted to the Environmental Quality Standards for heavy metals. Recent trends on trace metal speciation as well as on automatic "on line" monitoring devices are also evoked.

Keywords: carbon electrode; chemically modified electrode; electrochemical detection; heavy metals; ion selective electrode; mercury-free electrode; polarography; speciation.

Figure 1

DPASV voltammograms for increasing level of Cd and Pb in the 20–130 ppb range on porous Bi film (gold substrate) electrode. Reprinted with permission from Urbanova et al. (2010). Copyright 2010 Wiley-VCH.

Figure 2

Voltammograms for a-CNx (A) and BDD (B) in solutions containing different Cd²⁺ concentrations. Reprinted with permission from Seck et al. (2012). Copyright 2012 Wiley-VCH.

Figure 3

DPASV obtained with a BDD micromachined microcell on a standard solution of Cd (20 nM), Ni (38 nM), Pb (11 nM) and Hg (0.55 nM). Reprinted with permission from Sbartai et al. (2012). Copyright 2012 American Chemical Society.

Figure 4

Typical DPASV and calibration (inset panel) curves obtained for Cu²⁺ using a 10% amine functionalized silica film deposited on gold. Reprinted with permission from Walcarius and Sibottier (2005). Copyright 2005 Wiley-VCH.

Figure 5

(A) SW Voltammogram recorded every 12 h for 42 h analysis by semicontinuous flow injection of tap water doped with Cd (B) Variation of Cd and Pb peak currents over the 42 h. Reprinted with permission from Betelu et al. (2007). Copyright 2007 Wiley-VCH.

Figure 6

DPV curves recorded at a poly(EDTA-like) film modified carbon electrode in acetate buffer containing Hg(OAc)₂ (dotted line), Cu(OAc)₂, Cd(NO₃)₂, Pb(NO₃)₂, Hg(OAc)₂ (full line). Reprinted with permission from Buica et al. (2009b). Copyright 2009 Wiley-VCH.

Figure 7

AuNPs electrodeposited onto GC from a 0.25 mM HAuCl₄ solution using: (A) chronoamperometry; (B) potentiostatic double pulse; (C) cyclic voltammetry. (D) SWASV response and calibration curve obtained in the Hg(II) concentration range 0.8–9.9 nM using electrode (A). Adapted from our own results published in Hezard et al. (2012b), Copyright 2012 Elsevier.