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Pulsed and square wave voltammetry

Pulsed and square wave voltammetry. 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 1950-60s by

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Pulsed and square wave voltammetry

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  1. Pulsed and square wave voltammetry

  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 1950-60s by Sir Geoffrey Barker in UK, and later 1970-80s 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. Normal Pulsed Voltammetry (simplest) DL about 15-fold lower than cyclic voltammetry (CV) Input waveform output

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

  6. Square Wave Voltammetry – complex waveform, derivative output most sensitive instrumental electrochemical method Input waveform Ep nM detection limits; Slightly better than Differential pulse output

  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

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