Pulsed Voltammetric Techniques

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Pulsed Voltammetric Techniques

Typical Set up for Polarography

Pulsed Voltammetric Methods

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DC Polarography with Dropping Mercury Electrode (DME)

Pulsed Voltammetric Methods

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Sample-and-Hold or Tast (sampled-current) Voltammetry

Pulsed Voltammetric Methods

E

t

E

6/13/2*2/1708)( mCnDi OOd

3/13/2 )(00567.0)( EEmCi PZCid

Current is sampled late in the drop life, so faradaic current is minimized versus near onset.

LOD ~ 10-5 M

4 of 10Normal Pulse (NPV or NPP) vs. Tast Voltammetry

Pulsed Voltammetric Methods

Current sampled and held.

2/12/1

*2/1

)'()(

OO

NPVdCnFADi

' If > 5RsCd (~0.05-15 ms), icharging is almost insignificant. LOD ~ 10-5 -10-6M

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DPV

NPV

Differential Pulse (DPV) vs. Normal Pulse VoltammetryPulsed Voltammetric Methods

Small ifaradaic

when away from E0’

Large ifaradaic when near E0’

LOD ~ 10-6 -10-7 M

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NPV

DPV

OsteryoungSquareWaveVoltammetry

Comparison of Excitation Waveforms for Pulsed VoltammetriesPulsed Voltammetric Methods

8 of 10Osteryoung Square Wave Voltammetry Pulsed Voltammetric Methods

LOD ~ 10-8 M

9 of 10Osteryoung Square Wave Voltammetry

Pulsed Voltammetric Methods

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Stripping Analysis Coupled to DPV - DPASV

ip = 0.138 Qmetal/tpulse-width

~50-nm thick Hg film on Glassy Carbon (vitreous) electrode by electrodeposition from acidic Hg2+

DPVDeposit M0

Limit of Detection of ~0.005 ppm

Pulsed Voltammetric Methods