eDAQ Picostat, Руководство пользователя

Страница: 69 / 122

Chapter 5 — Techniques 65
Thus, by setting the data acquisition rate to be as fast as possible for a
particular experiment, you will also ensure that the waveform has steps
that are as small as possible.
When performing FCV, a large background charging current is often
recorded. This can be many times larger than the signal you are
looking for. Fortunately the charging current is usually reproducible
between scans and can be subtracted from the final result:
1. first a background scan is obtained with a ‘blank’ solution (that
is, a solution containing only the background electrolyte);
2. next a scan is performed of the solution in which the substrate is
present; and finally
3. the Scope ‘page’ that contains the background scan is selected
using the Display > Set Background command which will subtract
this scan from all other pages in the file. Use the Display > Don't
Subtract Background command to cancel subtraction, and Clear
Background to cancel the subtraction and clear the background
sweep.
The background scan must be run under the same conditions (sweep
width and stimulator settings) as the substrate solution to be effective.
See the
Scope Software Manual for more information.
Chronoamperometry with Chart
Chronoamperometric techniques require that a constant potential is
maintained for a defined period while the current is monitored. If the
current signal is integrated with respect to time then the total charge
transferred at the electrode can be calculated (
Chronocoulometry,
page 75 ).
Single, double and even multi-step chronoamperometry, can be
performed with Chart or Scope software, in a time frame from a
millisecond to hours, or even days, if need be. For experiments
involving sudden changes in potential you should use the full bandwidth
of the Potentiostat or Picostat, or QuadStat (that is, if possible, do not
use the low-pass filters) or the response of the current signal may be
modified by the low-pass filter time response characteristics.