As far as the effect of pulse duration/pulse interval ratio is concerned, an optimal combination of duration and interval is critical for reducing the overall processing time and energy. As it can be seen in Fig. 3, the extraction yield increased with decreased ratio, since a short interval indicates a short total processing time, which does not allow sufficient time for completing the mass transfer. After reaching equilibrium, the efficiencies were 38.6%, 36.2%, and 34.8%, for duration/interval ratio of 5/15, 7/6, and 2/1, respectively. A similar trend was reported by Roldán-Gutiérrez and Ruiz- Jiménez (2008) and Pan et al. (2012).