In order to achieve high ionic conductivity, electrochemical measurements are conducted in the presence of excess electrolyte.  In water the electrolyte is often a simple salt such as potassium chloride.  For measurements in nonaqueous solutions, salts composed of both lipophilic cations and anions are employed, e.g., tetrabutylammonium hexafluorophosphate.  Even in such cases potentials are influenced by ion-pairing, an effect that is accentuated in solvents of low dielectric constant.