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Modified electrodes used for electrochemical detection of metal ions in environmental analysis.

March G, Nguyen TD, Piro B - Biosensors (Basel) (2015)

Bottom Line: Heavy metal pollution is one of the most serious environmental problems, and regulations are becoming stricter.Many efforts have been made to develop sensors for monitoring heavy metals in the environment.Special attention will be paid to strategies using biomolecules (DNA, peptide or proteins), enzymes or whole cells.

View Article: PubMed Central - PubMed

Affiliation: Klearia, route de Nozay, Marcoussis 91460, France. gregory.march@free.fr.

ABSTRACT
Heavy metal pollution is one of the most serious environmental problems, and regulations are becoming stricter. Many efforts have been made to develop sensors for monitoring heavy metals in the environment. This review aims at presenting the different label-free strategies used to develop electrochemical sensors for the detection of heavy metals such as lead, cadmium, mercury, arsenic etc. The first part of this review will be dedicated to stripping voltammetry techniques, on unmodified electrodes (mercury, bismuth or noble metals in the bulk form), or electrodes modified at their surface by nanoparticles, nanostructures (CNT, graphene) or other innovative materials such as boron-doped diamond. The second part will be dedicated to chemically modified electrodes especially those with conducting polymers. The last part of this review will focus on bio-modified electrodes. Special attention will be paid to strategies using biomolecules (DNA, peptide or proteins), enzymes or whole cells.

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(A) Schematic diagram for the deposition and stripping processes. (a) The potential is maintained at −1.0 V where lead and copper deposits are formed but the latter are quickly covered by reduced lead. (b) When scanning in the positive direction, lead is first oxidized, (c) leaving copper deposits exposed, and hydrogen evolution takes place. (d) Continuing scanning at potentials E > 0.0 V Cu deposits are oxidized; (B) Three-dimensional calibration curves for the differential pulse anodic stripping currents for (a) Cd (II) (b) Pb (II) in acetate buffer solutions containing both metals. Reprinted from [64], with permission from Elsevier.
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biosensors-05-00241-f005: (A) Schematic diagram for the deposition and stripping processes. (a) The potential is maintained at −1.0 V where lead and copper deposits are formed but the latter are quickly covered by reduced lead. (b) When scanning in the positive direction, lead is first oxidized, (c) leaving copper deposits exposed, and hydrogen evolution takes place. (d) Continuing scanning at potentials E > 0.0 V Cu deposits are oxidized; (B) Three-dimensional calibration curves for the differential pulse anodic stripping currents for (a) Cd (II) (b) Pb (II) in acetate buffer solutions containing both metals. Reprinted from [64], with permission from Elsevier.

Mentions: The reason why BDD electrodes attract much attention for stripping analysis of heavy metals is that they can be used within a very wide potential window. Peilin et al. [49] demonstrated that BDD has a slightly better sensitivity for lead (3 nA·mm−2·ppb−1) than glassy carbon electrode (GCE) (2.4 nA·mm−2·ppb−1), when both use in situ plated mercury. However, BDD without mercury plating exhibits three to five times lower sensitivity compared to mercury plated GCE [50]. With ASV, Manivannan et al. have reported that sub-ppb detection of lead is achievable using −1 V deposition potential for 15 min [51,52,53]. Compton’s group has shown that sonoelectrochemical treatment increased sensitivity for Pb [54], Cd [55], Mn [56] and Ag [57]. BDD electrodes have been successfully used for the simultaneous detection of mixtures of HMs: Pb + Cd + Ag [58], Zn + Pb + Cd + Cu [59], Pb + Cd + Cu + Hg [60] and Cd + Ni + Pb + Hg [61]. Hutton et al. have examined the factors controlling stripping voltammetry of lead at BDD using high-resolution microscopy [62]. They have shown that the deposition process was driven to produce a grain-independent homogeneous distribution of Pb nanoparticles on the electrode and that substantial amount of Pb remains on the surface after stripping, which explains the non-linear response at high concentrations. Prado et al. studied the interaction between Pb and Cu [63] during simultaneous detection by ASV. They observed the appearance of an extra peak which was attributed to hydrogen evolution on copper. They suggested that Cu deposition occurs preferentially, then Pb deposition takes place on already formed copper deposits which act as active sites for nucleation and growth process. This covers the copper with a solid film of lead. During the stripping step, oxidation of lead takes place first, so the copper deposits would be suddenly exposed to an acid electrolyte at a potential at which hydrogen evolution could take place. Manivannan et al. [64] studied the interaction between Pb and Cd during simultaneous detection (Figure 5A). They observed that in the presence of a constant concentration of Pb (5 µM), the peak currents for Cd were ca. 55% smaller than those obtained without Pb. On the contrary, they also observed that in the presence of a constant concentration of Cd (5 µM), the peak currents for Pb were ca. 40% larger compared to those for Pb in the absence of Cd. This behavior was explained through the model described above for Pb and Cu, i.e., metals that have more negative standard potentials tend to deposit on metals that have less negative standard potentials. This explains the difference in peak current observed for Cd and Pb. The authors proposed a 3D calibration curve to avoid cross-interference between these two metals (Figure 5B).


Modified electrodes used for electrochemical detection of metal ions in environmental analysis.

March G, Nguyen TD, Piro B - Biosensors (Basel) (2015)

(A) Schematic diagram for the deposition and stripping processes. (a) The potential is maintained at −1.0 V where lead and copper deposits are formed but the latter are quickly covered by reduced lead. (b) When scanning in the positive direction, lead is first oxidized, (c) leaving copper deposits exposed, and hydrogen evolution takes place. (d) Continuing scanning at potentials E > 0.0 V Cu deposits are oxidized; (B) Three-dimensional calibration curves for the differential pulse anodic stripping currents for (a) Cd (II) (b) Pb (II) in acetate buffer solutions containing both metals. Reprinted from [64], with permission from Elsevier.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493548&req=5

biosensors-05-00241-f005: (A) Schematic diagram for the deposition and stripping processes. (a) The potential is maintained at −1.0 V where lead and copper deposits are formed but the latter are quickly covered by reduced lead. (b) When scanning in the positive direction, lead is first oxidized, (c) leaving copper deposits exposed, and hydrogen evolution takes place. (d) Continuing scanning at potentials E > 0.0 V Cu deposits are oxidized; (B) Three-dimensional calibration curves for the differential pulse anodic stripping currents for (a) Cd (II) (b) Pb (II) in acetate buffer solutions containing both metals. Reprinted from [64], with permission from Elsevier.
Mentions: The reason why BDD electrodes attract much attention for stripping analysis of heavy metals is that they can be used within a very wide potential window. Peilin et al. [49] demonstrated that BDD has a slightly better sensitivity for lead (3 nA·mm−2·ppb−1) than glassy carbon electrode (GCE) (2.4 nA·mm−2·ppb−1), when both use in situ plated mercury. However, BDD without mercury plating exhibits three to five times lower sensitivity compared to mercury plated GCE [50]. With ASV, Manivannan et al. have reported that sub-ppb detection of lead is achievable using −1 V deposition potential for 15 min [51,52,53]. Compton’s group has shown that sonoelectrochemical treatment increased sensitivity for Pb [54], Cd [55], Mn [56] and Ag [57]. BDD electrodes have been successfully used for the simultaneous detection of mixtures of HMs: Pb + Cd + Ag [58], Zn + Pb + Cd + Cu [59], Pb + Cd + Cu + Hg [60] and Cd + Ni + Pb + Hg [61]. Hutton et al. have examined the factors controlling stripping voltammetry of lead at BDD using high-resolution microscopy [62]. They have shown that the deposition process was driven to produce a grain-independent homogeneous distribution of Pb nanoparticles on the electrode and that substantial amount of Pb remains on the surface after stripping, which explains the non-linear response at high concentrations. Prado et al. studied the interaction between Pb and Cu [63] during simultaneous detection by ASV. They observed the appearance of an extra peak which was attributed to hydrogen evolution on copper. They suggested that Cu deposition occurs preferentially, then Pb deposition takes place on already formed copper deposits which act as active sites for nucleation and growth process. This covers the copper with a solid film of lead. During the stripping step, oxidation of lead takes place first, so the copper deposits would be suddenly exposed to an acid electrolyte at a potential at which hydrogen evolution could take place. Manivannan et al. [64] studied the interaction between Pb and Cd during simultaneous detection (Figure 5A). They observed that in the presence of a constant concentration of Pb (5 µM), the peak currents for Cd were ca. 55% smaller than those obtained without Pb. On the contrary, they also observed that in the presence of a constant concentration of Cd (5 µM), the peak currents for Pb were ca. 40% larger compared to those for Pb in the absence of Cd. This behavior was explained through the model described above for Pb and Cu, i.e., metals that have more negative standard potentials tend to deposit on metals that have less negative standard potentials. This explains the difference in peak current observed for Cd and Pb. The authors proposed a 3D calibration curve to avoid cross-interference between these two metals (Figure 5B).

Bottom Line: Heavy metal pollution is one of the most serious environmental problems, and regulations are becoming stricter.Many efforts have been made to develop sensors for monitoring heavy metals in the environment.Special attention will be paid to strategies using biomolecules (DNA, peptide or proteins), enzymes or whole cells.

View Article: PubMed Central - PubMed

Affiliation: Klearia, route de Nozay, Marcoussis 91460, France. gregory.march@free.fr.

ABSTRACT
Heavy metal pollution is one of the most serious environmental problems, and regulations are becoming stricter. Many efforts have been made to develop sensors for monitoring heavy metals in the environment. This review aims at presenting the different label-free strategies used to develop electrochemical sensors for the detection of heavy metals such as lead, cadmium, mercury, arsenic etc. The first part of this review will be dedicated to stripping voltammetry techniques, on unmodified electrodes (mercury, bismuth or noble metals in the bulk form), or electrodes modified at their surface by nanoparticles, nanostructures (CNT, graphene) or other innovative materials such as boron-doped diamond. The second part will be dedicated to chemically modified electrodes especially those with conducting polymers. The last part of this review will focus on bio-modified electrodes. Special attention will be paid to strategies using biomolecules (DNA, peptide or proteins), enzymes or whole cells.

Show MeSH