The Brownian motion of two particles confined near the bottom of a suspended droplet was considered in order to examine the electrical double-layer interaction between them. The mean distance between the particles was expressed as a function of the Debye screening length. We report the application of Brownian particle trajectories for the experimental determination of the Debye screening length between gold particles trapped within a water droplet. This was computed through a comparison of the mean distance measured by observing the Brownian motion with its theoretical value. (C) 2016 Elsevier B.V. All rights reserved.