In this study, the effect of the solution conductivity on the behavior of microalgal cells (Chlorella) with different lipid contents under a non-uniform electric field was investigated. It was found that, for the algal cells with 11 wt% lipid content, the crossover frequency is between 2 and 10 MHz when the solution conductivity is within 1.4 and 2.95 mS/cm, and increases as the solution conductivity increases. As to the microalgal cells with 45 wt% lipid content, they experienced negative DEP at frequency below 20 MHz when the solution conductivity is within 2.06 and 2.95 mS/cm. However, positive DEP was observed when the solution conductivity becomes 1.4 mS/cm. In a mixture of the algal cells, those with different lipid contents were successfully separated by DEP at solution conductivity of 2.95 mS/cm and frequency of 20 MHz. (C) 2012 Elsevier Ltd. All rights reserved.