eDAQ Picostat, User Manual

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84 eDAQ Potentiostats
operated in Galvanostat mode, is suitable for experiments where
currents less than 100 mA and potentials less than 10 V are
anticipated. (Please note that the Picostat, or QuadStat, cannot be
operated as a galvanostat). A constant current is applied between the
working and auxiliary electrodes and the potential at the working
electrode is monitored as the substrate is oxidized or reduced. As the
electrolysis continues the substrate is eventually completely consumed
and the potential will alter as the galvanostat tries to maintain a
constant current. Both the potential and the current flow can be
monitored with Chart software. The integrated current (that is, the total
charge transferred) can also be determined which can be used to
determine the extent of reaction.
Electrosynthesis and electropolymerization reactions are often more
quickly carried out under constant current conditions than under
constant potential conditions, but there is a greater risk of side reactions
occurring as the potential changes. Ideally there should no competing
redox reactions at nearby potentials.
A sudden change in the potential usually indicates when the substrate is
fully consumed.
It is important to limit the current so that the potential stays within the
compliance voltage (10 V) of the Potentiostat/Galvanostat, at least until
the reaction of interest is complete. Electropolymerization reactions can
be problematic as a non-conducting polymer film adhering to the
working electrode will increase its electrical resistance causing the
Potentiostat to eventually go out of compliance and experience a
potential overload.
Amperometric Sensors
Amperometric sensors require a potentiostat of appropriate gain range.
Your will also need to determine whether the sensor is of a two or three
electrode configuration. The Potentiostat (up to 100 nA), Picostat (up to
100 nA), and QuadStat (up to 1 mA) can be used in three electrode
mode (working, reference and auxiliary electrode), or in two electrode
mode (working and counter electrodes) by connecting the reference
and auxiliary leads of the electrode cable together. You will also need
to determine the correct ‘polarising voltage’ to use with your sensor.