Square-wave Voltammetry Experimental Sequence

  1. The Framework creates a runner window, and theSquare Wave Voltammetry.expscript is run in this window.

  2. The script creates the Setup dialog box, which becomes the active window and accepts changes in the experimental parameters. This Setup box remembers the experimental settings from the last time this script was run. To restore the parameters to the values defined in the script, click the Default button. If the Advanced Pstat Setup is on, a second Setup dialog box containing hardware-configuration details becomes the active window, so you can modify the hardware configuration.

  3. The script now obtains the use of the potentiostat and opens the data file using the Output File name. If the potentiostat is in use, or the file cannot be opened, the script returns you to the Setup dialog box.
  4. All header information is written to the data files. Header information consists of the analysis tag, the time and date the experiment was started, and a list of the setup parameters.
  5. If you selected a purge time greater than zero, the potentiostat's control bits for purge-gas flow and stirring are turned on. The script delays for the purge time, then turns OFF the stirring and purge-gas control bits.
  6. If the electrode is an HDME, a new drop is formed by momentarily activating the potentiostat's New Drop control bit.
  7. The script delays for a time set by the Quiet Time parameter.

  8. The potentiostat is initialized. The current range is set to a range that allows the measurement of currents as big as the value of the Max I Setup parameter.

  9. The current range is set to a range that allows the measurement of currents as big as the value of the Max I Setup parameter.

  10. Finally the actual scan occurs.

  11. N is the number of steps that have already occurred. At the start of the scan N is zero.

  12. The potential of the sample is set to the staircase potential (Initial E plus N times the step height) plus the pulse size. This potential is applied for half the period of the square wave. At the end of this time, a current measurement is made. The sign of the pulse size is controlled, so that the pulse is always in the direction of the final potential.

  13. A voltage equal to two times the pulse height is subtracted from the cell voltage. This voltage is equivalent to Initial E plus N times the step height minus the pulse size. This new voltage is held for half the square-wave period. At the end of this time, a current measurement is made.

  14. The difference between the second and first current measurement (I1 – I2) is calculated and plotted versus the staircase potential.

  15. If Autoranging was selected in Setup and the SWV frequency is less than 50 Hz, after each point the current range is automatically switched to the optimal range for the measured cell currents.

  16. Steps 12 through 15 are repeated until the staircase potential equals the final potential.

  17. The cell is turned off. The script pauses to allow you to admire the curve you have just collected.