Mechanochemical-assisted extraction of essential oils from Citrus aurantium L. var. amara Engl.

Mechanochemistry is a process that could convert mechanical energy into the substance's internal energy to induce changes. In the current study, mechanochemistry was employed for the first time to extract the essential oil from Citrus aurantium L . var. amara Engl . Materials and reagents were ground at high speed in a planetary ball mill and exposed to solvent extraction. To achieve the best extraction from Citrus aurantium L . var. amara Engl . , the following parameters were selected: 5% fumed silica A200 as solid reagent, ball milling at 300 r/min for 10 min and extraction with n-hexane (1 g/5 mL) during 30 min. These settings gave an essential oil yield of 6.60 ± 0.20%. This is 26 times higher than by hydrodistillation (0.25 ± 0.03%) and more than 3 times higher compared to reflux extraction (2.08 ± 0.16%). The extracts obtained by the three approaches were analysed applying GC-MS. A total of 65 components was identified, including 60 by mechanochemical-assisted extraction, 27 by hydrodistillation and 49 by reflux extraction. Furthermore, scanning electron microscopy was used to observe the changes in material surface structure by the effect of mechanochemical-assisted extraction.