Knowledgebase

The purpose of this webpage is to show the effect of choosing the wrong electrode range for an experiment. This example is from cyclic voltammetry but is applicable to any technique that sweeps the potential of the working electrode.

Consider a 1 mM solution of K₃Fe(CN)₆ in 0.1 M KCl (3 mm disc GC working electrode and sweep rate 100 mV/s). The Electrode Range on the Basic tab is used to specify the expected range of current. If the choice of electrode range is too small (e.g. 10 μA), actual current may go off scale and be truncated (see Figure 1, red trace). If the electrode range is too large (e.g. 5 mA), the voltammogram may have a noisy, choppy, or quantized appearance (see Figure 1, black trace). When the electrode is set to the appropriate range (e.g. 200 μA), the voltammogram appears smooth (see Figure 1, green trace).

Some Pine potentiostats (such as the WaveNow and WaveNano portable USB potentiostats) have current autoranging capability. To take advantage of this feature, set the electrode range parameter to “Auto”. This allows the potentiostat to choose the current range “on-the-fly” while the voltammogram is being acquired.

Figure 1: Influence of Current Range Choice on Voltammogram Quality

Links: Electrochemist's Guide, AfterMath User's Guide, AfterMath Main Support Page