categories of such sensors: Anodic Stripping Voltammetry (ASV) and Adsorptive
Cathodic Stripping Voltammetry (ASCV).
ASV is the most common, highly reliable and well established method. It
employs electrodes such as Hanging Mercury Drop Electrode (HMDE) and
Mercury film electrodes (MFE). In HMDE new drops are created in each test which
leads to creation of new electrode surface. This increases the reliability of the results
obtained in case of these electrodes. MFE are more robust and highly selective than
HMDE due to their high surface to volume ratio. The deposition potential of −0.3
or lesser (less than reduction potential of analyte) is applied during preconcentration
and reverse scan is performed towards more positive potential. This leads to oxidation of metal in mercury. Peak oxidation potential give the information about the
analyzed metal and peak intensity is related to the metal concentration [30]. The
equation can be given as:
M
n þ + ne
À + Hg M Hg
ð Þ
Mercury electrodes are useful for a range of metal ions and MFE are more
selective than HMDE. The smaller volume of MFE leads to more collection of
metal into the mercury. These electrodes are covered with agarose membrane as an
antifouling agent. They are useful in detection of metal ions such as Lead, copper,
cadmium etc. in water samples [31]. Since mercury tends to have environmental
toxicity issues, researches are being carried out on other materials based electrode
systems. Some of the modified electrodes for Voltammetric sensors can be summarized in the Table 1.
Table 1 Electrode modifications for voltammetric sensing techniques
Analyte
Electrode modification
References
Pb
2+ , As
3+
ASV
Gold Electrode (Good electrochemical inertness
due to larger cathodic potential)
[32, 33]
Pb
2+ , Cd
2+
and Cu
2+
MFE microelectrode (Extraordinary detection
limit)
[32]
Hg
2+
Au-Pt electrode and Au on Graphene electrode
(High resistance to chemical reaction)
[34, 33]
Fe
2+ , Zn
2+ ,
Pb
2+ , Cu
2+
Amalgam electrodes (best cathodic potential
window)
[35, 36]
Co
2+ , Cr
6+
AdCSV
HMDE (smooth and uncontaminated surface
which is self-renewing)
[37, 38]
Co
2+ , Cr
6+ ,
Ni
2+
Bismuth film electrode (environment friendly as
compared to Hg and combine with metals just
like mercury form amalgams)
[39–41]
U
6+
Bismuth coated carbon fiber electrode (High
reproducibility of results)
[40, 41]
Imidacloprid,
Acetamiprid
Bismuth film electrode
[42]
Materials in Electrochemical Detection of Water Pollutants
167
Cathodic Stripping Voltammetry (ASCV).
ASV is the most common, highly reliable and well established method. It
employs electrodes such as Hanging Mercury Drop Electrode (HMDE) and
Mercury film electrodes (MFE). In HMDE new drops are created in each test which
leads to creation of new electrode surface. This increases the reliability of the results
obtained in case of these electrodes. MFE are more robust and highly selective than
HMDE due to their high surface to volume ratio. The deposition potential of −0.3
or lesser (less than reduction potential of analyte) is applied during preconcentration
and reverse scan is performed towards more positive potential. This leads to oxidation of metal in mercury. Peak oxidation potential give the information about the
analyzed metal and peak intensity is related to the metal concentration [30]. The
equation can be given as:
M
n þ + ne
À + Hg M Hg
ð Þ
Mercury electrodes are useful for a range of metal ions and MFE are more
selective than HMDE. The smaller volume of MFE leads to more collection of
metal into the mercury. These electrodes are covered with agarose membrane as an
antifouling agent. They are useful in detection of metal ions such as Lead, copper,
cadmium etc. in water samples [31]. Since mercury tends to have environmental
toxicity issues, researches are being carried out on other materials based electrode
systems. Some of the modified electrodes for Voltammetric sensors can be summarized in the Table 1.
Table 1 Electrode modifications for voltammetric sensing techniques
Analyte
Electrode modification
References
Pb
2+ , As
3+
ASV
Gold Electrode (Good electrochemical inertness
due to larger cathodic potential)
[32, 33]
Pb
2+ , Cd
2+
and Cu
2+
MFE microelectrode (Extraordinary detection
limit)
[32]
Hg
2+
Au-Pt electrode and Au on Graphene electrode
(High resistance to chemical reaction)
[34, 33]
Fe
2+ , Zn
2+ ,
Pb
2+ , Cu
2+
Amalgam electrodes (best cathodic potential
window)
[35, 36]
Co
2+ , Cr
6+
AdCSV
HMDE (smooth and uncontaminated surface
which is self-renewing)
[37, 38]
Co
2+ , Cr
6+ ,
Ni
2+
Bismuth film electrode (environment friendly as
compared to Hg and combine with metals just
like mercury form amalgams)
[39–41]
U
6+
Bismuth coated carbon fiber electrode (High
reproducibility of results)
[40, 41]
Imidacloprid,
Acetamiprid
Bismuth film electrode
[42]
Materials in Electrochemical Detection of Water Pollutants
167