Although there were some other factors which were not studied
here such as the sample particle size and the solvent flow rate, the
authors have reported them in other Refs. [12,13], In these previous
studies, it was found that the oil yield increased with decreasing
particle size if the intra-particle diffusion had taken control of
the oil transfer during the extraction process. Although the oil yield
increased with increasing the solvent flow rate at the same
extraction time, the solubility of oil was not a function of CO2 flow
rate