An improved approach for the isolation of essential oil from the leaves of Cinnamomum longepaniculatum using microwave-assisted hydrodistillation concatenated double-column liquid-liquid extraction

In this work, an improved method was developed to isolate essential oil from the leaves of Cinnamomum longepaniculatum, i.e., microwave-assisted hydrodistillation concatenated double-column liquid-liquid extraction, including the traditional essential oil-water separation process and the extraction process of essential oil components dissolved in water using an organic solvent in the second and third separation columns. The selection of extraction solvent indicated that ethyl ether performed better than other solvents, and the addition of glass beads as the filter in the separation columns had great advantage for extraction of essential oil components because of the larger contact area. The investigation on the number of separation column indicated that double liquid-liquid extraction column was better for improving the essential oil yield. After detailed optimization, the optimum conditions were homogenate time of 2.9 min, microwave irradiation time of 23 min and microwave irradiation power of 540 W (specific absorbed power: 1.27 W/g). Satisfactory yields of essential oil in the three separation columns (29.04 ± 0.87, 2.03 ± 0.07 and 0.90 ± 0.03 g/kg) were obtained under these conditions. The kinetic curves of various microwave irradiation powers based on the total yield of essential oil versus time were described. In addition, the kinetics curves of the developed method and other traditional methods were fitted by first-order model for comparison. The essential oil extracted in the second and third separation columns mainly contained oxy-compounds through GC-MS analysis, which could provide special values for application.