2. VOLTAMMETRY
• Voltage ramp applied to
electrode.
• Current measure
• Reduces ions in the electrode
• Commonly uses three
electrodes
1. Working Electrode (WE)
2. Auxiliary Electrode (AE)
3. Reference Electrode (RE)
Voltammetry is an electrochemical method in which
information about an analyte is obtained by current.
3. Working Electrode(WE)
The working electrode is the electrode is in the electrode in
an electrochemical system on which the reaction of interest
is occurring.
The WE is often used in conjunction with an auxiliary
electrode.
• Types of WE
– Glassy carbon
– Gold
– Platinum
– Mercury
4. Auxiliary Electrode(AE)
The auxiliary electrode ,often also called counter
electrode, used in a voltammetric analysis in which
an electric current is expected to flow.
Completes the circuit between the potentiostat and
the WE
• Two different types available.
– Platinum
– Glassy Carbon
5. Reference Electrode(RE)
• A reference electrode is an electrode which
has a stable and well known electrode
potential.
• Provides a reference potential to the WE/AE
circuit
• Two types of RE
– Ag/AgCl in KCI
– Hg/HgCl in saturated KCI
6. Working electrode: Microelectrode
whose potential is varied with time
Reference electrode: Potential
remains constant (Ag/AgCl electrode
or calomel)
auxiliary electrode: Hg or Pt that
completes circuit, conducts e-
from
signal source through solution to the
working electrode
Supporting electrolyte: excess of
nonreactive electrolyte (alkali metal) to
conduct current
Instrumentation
Three electrodes in solution containing analyte
8. CYCLIC VOLTAMMETRY(CV)
Cylic voltammtry is an electrochemical technique which
measures the current that devlops in an electrochemical cell
under condition where voltage is in excess of that predicted
by the Nernst equation.
CV is performed by clicking the potential of a working
electrode,and measuring the electric current.
9. SQUAREWAVE VOLTAMMETRY(SWV)
Squarewave voltammetry is a form of linear
potential sweep voltammtery which has found
numerous applications in various fields.
When first reported by barker in 1957, the working
electrode utilized was primarily a dropping mercury
electrode(DME).
10. DIFFERENTIAL PULSE VOLTAMMTRY
• Differential pulse voltammetry is often used to make
electrochemical measurments.
• The current is measured immediately before each
potential change,and the current difference is plotted as a
function of potential.
11. STRIPPING VOLTAMMETRY
Stripping voltammetry is a voltammteric method for
quantitative determination of specific ionic species.
This technique is used for ionic species that form
insouluble salt.
12. -0.2 -0.4 -0.6 -0.8 -1.0 -1.2 -1.4
i (µA)
Potential applied on the working electrode is usually swept over (i.e. scan)Potential applied on the working electrode is usually swept over (i.e. scan)
a pre-defined range of applied potentiala pre-defined range of applied potential
0.001 M Cd2+
in 0.1 M KNO3 supporting electrolyte
V vs SCE
Working electrode is
no yet capable of
reducing Cd2+
⇒
only small residual
current flow through
the electrode
Electrode become more and more
reducing and capable of reducing Cd2+
Cd2+
+ 2e-
Cd
Current starts to be registered at the
electrode
Current at the working
electrode continue to rise as
the electrode become more
reducing and more Cd2+
around
the electrode are being
reduced. Diffusion of Cd2+
does not limit the current yet
All Cd2+
around the electrode has
already been reduced. Current at
the electrode becomes limited by
the diffusion rate of Cd2+
from the
bulk solution to the electrode.
Thus, current stops rising and
levels off at a plateauid
E½
Base line
of residual
current
13. APPLICATIONS
• Determination of metal ion concentration in
water to sub parts per billion level.
• Wastewater Analysis
• Pharmaceuticals analysis
• Environmental Studies
• Biological/Biochemical Analysis
• Plating Analysis
14. • Handles high salt concentrations better
than chromatographic instrumentation
• Extremely low detection limits
• Can detect a wide range of species
