Differential Pulse Polarography
Differential Pulse Polarography is an electrochemical technique commonly called Differential Pulse Voltammetry at PalmSens.
In Differential Pulse Polarography a potential scan is made using pulses with a constant amplitude of E pulse superimposed on the dc-potential. The amplitude is mostly in the range of 5 – 50 mV.
The interval time between the pulses is equal to E step / scan rate. The current is sampled twice in each step: one time just before applying the pulse and one time at the end of the pulse. The difference between these two current samples is plotted versus the potential. The obtained current is proportional to the derivative of the curve obtained using linear sweep or normal pulse voltammetry. A DPV thus has a peak-shaped curve. The peak height is (normally) proportional to the concentration in the solution. Be aware that the peak is not the redox potential! E peak = E½ – E pulse / 2.
As in Normal Pulse Voltammetry (NPV) the diffusion layer thickness increases with pulse time, the current will be lower when the pulse time is increased. However, a short pulse time will result in an increased capacitive current and therefore give a higher (non-linear) baseline. In trace analysis, it is important to apply pulses with optimal pulse times. In general, the optimal value must be found by varying the pulse time.
Read more about this technique and related instruments in the article on Differential Pulse Voltammetry.Differential Pulse Voltammetry