All potential values are entered in mV, and the Step Width is entered in ms.
If the Apply Open Circuit Potential for Initial E box is checked, then the open circuit potential will automatically be measured and used as the Initial Potential.
If the Run - External Trigger box is checked, the experiment is started from an external device using the Start In back-panel connection.
The Pulse Type must be specified when using a mercury electrode (CGME SMDE Mode selected in the Cell Stand dialog box). If Voltammetry is selected, the whole experiment is performed on a single mercury drop (after the Pre Run Drops); if Polarography is selected, a new drop is used for each data point.
The change in the applied potential for each step is defined by Step E.
The Scan Rate cannot be directly changed by the user, and is determined by Step E x 1/Sample Width.
Three options are available for the Sample Period:
The current is measured once at the end of the Step Width (1 Point)
The current is measured multiple times in 1 ms at the end of the Step Width, and averaged (1 mSecond)
The current is measured multiple times over 1 line cycle at the end of the Step Width, and averaged (1 Line Period). The time required for 1 line cycle is the reciprocal of the line frequency (16.7 ms for 60 Hz, and 20 ms for 50 Hz). The line frequency is selected in the Setup / Manual Settings (I/O) dialog box.
Generally speaking, increasing the Sample Period increases the signal-to-noise ratio. However, the 1 Line Period option may not be possible for short Step Width values.
If the Apply Open Circuit Potential for Initial E box is checked, then the open circuit potential will automatically be measured and used as the Initial Potential.
When the experiment is started, the cell is held at the Initial Potential for the number of seconds defined by the Quiet Time.
There are two gain stages for the current-to-voltage converter. The default values of these stages that are used for a given current Full Scale value are determined by the software. However, they can be adjusted manually using the Filter / F.S. dialog box. This dialog box is also used to change the analog Noise Filter Value settings from the default values set by the software.
The default condition of the cell is that the cell is On (i.e., the electronics are connected to the electrodes) during the experiment, and is Offbetween experiments. However, the potential can be switched Onbetween experiments using the Cell dialog box. HOWEVER, THIS OPTION SHOULD BE USED WITH CAUTION SINCE CONNECTING OR DISCONNECTING THE ELECTRODES WHEN THE CELL IS ON CAN RESULT IN DAMAGE TO THE POTENTIOSTAT, THE CELL, AND/OR THE USER!
A series of identical experiments on the same cell can be programmed using the MR (Multi-Run) option.
Clicking Exit will exit the dialog box without saving any changes made to the parameter values. Any changes can be saved by clicking Apply before exiting.
Range of allowed parameter values:
Potential = -3275 - +3275 mV
Step E = 1 - 40 mV
Step Width = 100 - 6550 ms (Polarography); 4 - 6550 ms (Voltammetry)
Quiet Time = 0 - 100 s
Once the parameters have been set, the experiment can be started by clicking Run (either in this dialog box, in the Experiment menu, in the pop-up menu, on the Tool Bar, or using the F5 key).
The current response for SCP is shown in Fig3. The limiting current (id) is given by the Ilkovic equation:
id = 708nCD1/2m2/3t1/6
where: n = number of electrons transferred/molecule
C = concentration (mol cm-3)
D = diffusion coefficient (cm2 s-1)
m = mercury flow rate (mg s-1)
t = sampling interval (s)