What is (approximately) the minimum exchange current for a potentiometric measurement?
Pfeiffer at al. defines sensor effective (SERC) and sensor ineffective redox couples (SIRC) in relation to the biggest net exchange current found in the system $\text{i}_{net}$.

$\text{SERC} \geq 0.01~\text{i}_{net}$

$\text{SIRC} &lt; 0.01~\text{i}_{net}$

DOI: 10.1016/0169-7722(92)90041-C