The difference between the current that is actually obtained, at any particular value
of the potential of the
indicator or
working electrode, for the reduction or
oxidation of an ionic
electroactive substance and the current that would be obtained, at the same potential, if there were no transport
of that substance due to the electric field between the electrodes. The sign convention
regarding current is such that the
migration current is negative for the reduction of a
cation or for the
oxidation of an
anion, and positive for the
oxidation of a
cation or the reduction of an
anion. Hence the
migration current may tend to either increase or decrease the total current observed. In any
event the
migration current approaches zero as the
transport number of the
electroactive substance is decreased by increasing the concentration of the
supporting electrolyte,
and hence the
conductivitySource:
PAC, 1985, 57, 1491
(Recommended terms, symbols, and definitions for electroanalytical chemistry (Recommendations
1985))
on page 1497