Dielectrophoresis can be applied to capture specific particles from particle mixture dispersed in a liquid. In this study, the motion of graphite particles mixed with TiO2 particles dispersed in ethanol is observed in a dielectrophoretic condition. It has been found that a particle chain of graphite is first formed, and TiO2 particles are attracted to the graphite particle chain afterward. The electric field profile has been calculated around a modeled graphite particle chain which is a conductive needle to observe the influence of the particle chain length on the DEP force qualitatively. This calculation reveals that the gradient of square of the electric filed strength at the particle chain can become significantly larger when the particle chain is longer. This result suggests that TiO2 particles are attracted to the well-grown graphite particle chain even when TiO2 particles are hardly attracted to the pristine electrodes. Namely, to keep high selectivity in the collection of target particles, the duration time for the dielectrophoretic separation should not be excessively long in order to interrupt particle chain growth to avoid the attachment of impurity particles.