Chronocoulometry Experimental Sequence

The Spectro Chronocoulometry technique is run by selecting the Named Script command under the Experiment menu in Gamry’s Framework™. Opening the Spectro Chronocoulometry.exp file initiates the following sequence of events:

  1. Framework creates a runner window, and the Spectro Chronocoulometry.EXP script 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 with hardware configuration details becomes the active window, allowing you to modify the hardware configuration used during the experiment.
  3. The script next obtains the use of the potentiostat specified during Setup. The script opens a data file using the Output File name and a second data file using the prefix SpectraFor_ followed by the Output File name. This first file contains data for the chronocoulometric measurement and links to the second file which includes the spectra data.If the potentiostat is in use or the file cannot be opened, the script returns you to the Setup dialog box.
  4. The file header information is written to the data file prior to data-acquisition. If the experiment is aborted, the output file contains only this information. This header information includes: Tags identifying possible analyses, the current time and date, a list of the Setup parameters and hardware configuration. The header information for the spectroscopy file includes: Tags identifying possible analyses, and a list of setup parameters
    1. The measurement starts if Raw Counts is selected as Spectroscopy Type (skip to number 6). The Need to acquire Dark and Blank Spectra window appears if Absorbance or Transmittance is selected as Spectroscopy Type. You can decide if a dark and a blank spectrum should be recorded prior to the actual measurement:

a. If you click the OK button, the Acquire Dark Spectrum window appears.

By clicking OK again, a dark spectrum is recorded. The data of the dark spectrum are not saved. The Acquire Blank Spectrum window appears.

By clicking OK, a blank spectrum is recorded. The data of the blank spectrum are not saved. A Runtime Warning appears.

b. If you click the Cancel button, no dark or blank spectra are recorded. For the actual measurement, Raw Counts are measured and plotted versus wavelength.

    1. If  Initial Delay is on, the cell is turned off and the specimen’s Eoc is measured for the time specified as the Initial Delay time or until the potential stabilizes to a value less than the stability setting. The last measured potential is recorded as Eoc.

A plot of potential versus time is always displayed. A second window for the spectra shows no plot.

If Initial Delay is off, this step is skipped and Eoc is assumed to be 0.0 V vs. Ref.

  1. The script conditions the electrode if Conditioning was specified in the Setup. Conditioning is done by applying a fixed potential for a defined time with the stirrer turned on. A plot of current versus time is displayed during the Conditioning. No data are saved during this step.
  2. The electrode and the solution are allowed to equilibrate for a defined time. The cell is turned on, the Pre-step Voltage is applied, and the stirrer is off. No data are saved during this step.
  3. Finally the data-acquisition process starts. The potential of the sample is held at the Pre-step Voltage for the Pre-step delay. This information is stored with the data file and is intended to show that the user has selected a voltage where no appreciable current occurs. The potential is then stepped to Step 1 Voltage and held at that value for Step 1 time. The potential is then stepped to Step 2 Voltage and held at that value for Step 2 time. If Step 2 time is zero then the second step is skipped. Charge and current readings at fixed time intervals (Sample Period) are taken during the steps in Chronocoulometry. If you selected Autoranging in Setup, at each point the current range is automatically switched to the optimal range for the measured cell current. If Positive Feedback IR Compensation has been selected, all data are continuously corrected for IR-drop. If Current Interrupt IR Compensation has been selected, each potential is corrected for the measured IR-drop of the preceding point. Plots of Q and I vs. time are displayed during the steps.
  4. The data are written to the output file and the script cleans up and halts. When the scan is over, the cell is turned off. The acquired data are written to the output file. The script then waits for you to click the Skip button. When you do so, the script closes everything that’s open, including the runner window.