Herein, for the first time, research on water-in-oil (water/oil) emulsion droplets by electrochemical analysis has been reported. When the water/1,2-dichloroethane emulsion droplets collided with an ultramicroelectrode (UME), the blocking property of the droplets resulted in a "staircase" current decrease. Each "staircase" current decrease is associated with the collision of an emulsion droplet with the UME surface. The experimental collision frequency was proportional to the concentration of the emulsion droplet. In addition, the size of each water droplet was estimated from the magnitude of the "staircase" current decrease and the simulation data. Results obtained from the collision signals provide information about the size of each single droplet (nano-to micro-) and the pM level concentrations of the water droplets in the organic continuous phase. (C) 2017 Elsevier Ltd. All rights reserved.