Current-time (A) and observed potential-time (B) responses of flash chronopotentiometry experiment in the presence of 100 µg/ml protamine in a background of 10 mM phosphate containing 10 mM NaCl at pH 7.4. (1), (2) and (3) show uptake current pulse, zero current pulse and baseline potential pulse, respectively. i indicates the inflection point in the potential-time curve when ion depletion occurs, while ii and iii show sampled potentials at the end of the applied current pulse and zero current pulse, respectively.