AdCSV method is very sensitive and is effective for analysis of many trace
metals in water bodies. Ligands are added for inducing adsorptive quality to the
electrode. They form complexes with the metal ions. This adsorption is the preconcentration step and denotes selectivity as well as fast response time to the
electrodes. Adding buffer solution to the electrolyte for maintain pH as complexes
formation is pH dependent phenomenon. Adsorption potential slightly greater than
reduction potential of metal-ligand complexes (0.1 V) is applied. Reverse
Voltammetric scan is performed for reducing metal from the complexes. Peak
intensity and peak potential are used to determine type and concentration of metal
being investigated. AdCSV mainly employs both types of electrode (HMDE and
MFE) where HMDE is mostly used one. They have very small adsorptive time and
therefore can be used for fast detection of metal ions even at very low concentration
[37–39]. Bismuth film electrodes are Nano-level sensing devices that are useful for
interference free, on-site monitoring of pollutants such as U(VI) ions [40, 41].
2.4 Amperometric/Coulometric
They consist of two or three electrode systems that are dipped into an electrolytic
solution. The diffused analyte species are measured on the surface of working
electrode. Both Amperometric and Coulometric sensors work on the similar principle of applying a constant potential and measuring the current changes with time.
The current obtained is related to the concentration of analyte. The basic difference
between both of them is while in Amperometric sensors the fraction of electrolyzed
species is much lesser than one, its equal to unity in case of Coulometric sensors.
The most basic example of such sensor are one with Clark type electrodes (made of
Pt electrodes). The electrode is modified by various forms for getting selectivity and
stability [43]. Interferences are reduced by using Nafion coatings. Similarly for
different types of analyte coatings are used which are explained in Table 2.
Some of the modified forms of above mentioned techniques includes cyclic
voltammetry (measuring the resulting current on cycling the potential of the
working electrode), chrono-amperometry (current is measured as a function of time
at constant potential) and chrono-potentiometry (potential is measured as a function
of time at constant current), electrochemical impedance spectroscopy (measures the
changes of interfacial property of electrodes), and field effect transistors (electric
field is used to control the effect of current):
• Cyclic voltammetry: Measurement of periodic variation in voltage variation
with change in current (potentiodynamic electrochemical measurement technique). It involves ramping of electrode potential with time in cyclical manner.
The variations in voltage are done in wide variety of patterns that gives rise to
various methods of voltammetric analysis. This technique includes methods
such as polarography, linear sweep voltammetry (LSV), differential staircase
voltammetry (DSV), normal pulse, reverse pulses and differential pulses [3].
168
A. Ojha
metals in water bodies. Ligands are added for inducing adsorptive quality to the
electrode. They form complexes with the metal ions. This adsorption is the preconcentration step and denotes selectivity as well as fast response time to the
electrodes. Adding buffer solution to the electrolyte for maintain pH as complexes
formation is pH dependent phenomenon. Adsorption potential slightly greater than
reduction potential of metal-ligand complexes (0.1 V) is applied. Reverse
Voltammetric scan is performed for reducing metal from the complexes. Peak
intensity and peak potential are used to determine type and concentration of metal
being investigated. AdCSV mainly employs both types of electrode (HMDE and
MFE) where HMDE is mostly used one. They have very small adsorptive time and
therefore can be used for fast detection of metal ions even at very low concentration
[37–39]. Bismuth film electrodes are Nano-level sensing devices that are useful for
interference free, on-site monitoring of pollutants such as U(VI) ions [40, 41].
2.4 Amperometric/Coulometric
They consist of two or three electrode systems that are dipped into an electrolytic
solution. The diffused analyte species are measured on the surface of working
electrode. Both Amperometric and Coulometric sensors work on the similar principle of applying a constant potential and measuring the current changes with time.
The current obtained is related to the concentration of analyte. The basic difference
between both of them is while in Amperometric sensors the fraction of electrolyzed
species is much lesser than one, its equal to unity in case of Coulometric sensors.
The most basic example of such sensor are one with Clark type electrodes (made of
Pt electrodes). The electrode is modified by various forms for getting selectivity and
stability [43]. Interferences are reduced by using Nafion coatings. Similarly for
different types of analyte coatings are used which are explained in Table 2.
Some of the modified forms of above mentioned techniques includes cyclic
voltammetry (measuring the resulting current on cycling the potential of the
working electrode), chrono-amperometry (current is measured as a function of time
at constant potential) and chrono-potentiometry (potential is measured as a function
of time at constant current), electrochemical impedance spectroscopy (measures the
changes of interfacial property of electrodes), and field effect transistors (electric
field is used to control the effect of current):
• Cyclic voltammetry: Measurement of periodic variation in voltage variation
with change in current (potentiodynamic electrochemical measurement technique). It involves ramping of electrode potential with time in cyclical manner.
The variations in voltage are done in wide variety of patterns that gives rise to
various methods of voltammetric analysis. This technique includes methods
such as polarography, linear sweep voltammetry (LSV), differential staircase
voltammetry (DSV), normal pulse, reverse pulses and differential pulses [3].
168
A. Ojha