1. Inventor: Sir Geoffrey Barker, Harwell, UK 1950-60s
Pulsed and square wave voltammetry
Inventor: Sir Geoffrey Barker, Harwell, UK s
Modern versions. Janet and Robert Osteryoung, Univ. Colorado/SUNY Buffalo

2. Digital voltammetry waveforms – staircase used to approximate a ramp for LSV;
All modern potentiostats use this approach, also easy to use other input waveforms
All sorts of pulsed voltammetry methods were developed in s by
Sir Geoffrey Barker in UK, and later s modernized by Janet and Bob
Osteryoung in the US

3. Basis of all pulsed methods: Response of reversible system to a potential pulse;
Measuemenst at end of pulse discriminates against charging current E
60 ms
time
measurement
Faradaic I
Charging (decays faster)

4. I = IL/(1+θ) θ = {nf/RT)(E-Eo’)} IL=nFCo*AD1/2/(πt)1/2
Normal Pulsed Voltammetry (simplest) DL about 10-fold lower than cyclic voltammetry (CV)
Input waveform
output
I = IL/(1+θ)
θ = {nf/RT)(E-Eo’)}
IL=nFCo*AD1/2/(πt)1/2

5. Input waveforms
output
Normal pulse voltammetry
Differential Pulse voltammetry Ep
nM detection limits

6. Ip= f(Co*, ΔE) Ep= E1/2 – ΔE/2
Square Wave Voltammetry – complex waveform, derivative output most sensitive instrumental electrochemical method
Input waveform
Ip= f(Co*, ΔE)
Ep= E1/2 – ΔE/2
output Ep
nM detection limits;
Slightly better than
Differential pulse

7. SWV outputs
Net or difference current
Forward
Current
Reverse current

8. NPV
SWV
difference current
I x 1000
O1 + e == R1
R1 + e == R2
Better resolution,
Best sensitivity

9. SWV Output
Net or difference current
forward
reverse

10. SWV parameters - increasing frequency (effect of DE is similar)

11. Approx DL
NPV
10-6 M/n
DPV
2x10-9 M/n
SCV or LSV
(CV)
5x10-5 M/n
SWV
10-9 M/n