Rectification extraction of Chinese herbs’ volatile oils and comparison with conventional steam distillation

Rectification is a very efficient technique for gas–liquid separation and has being widely applied in the fields of chemical, petrochemical engineering, etc. In order to explore adaptability of using rectification extraction (RE) to isolate volatile oils from Chinese herbs, RE and steam distillation (SD) techniques were applied to isolate volatile oils from three typical Chinese herbs Bupleurum, Pogostemon cablin (Blanco) Benth (PCB), Pericarpium Citri Reticulatae (PCR) in this paper. The experiment shows that SD technique cannot get volatile oils and only aromatic water from Bupleurum but RE can prepare both. RE technique increases 10% oil yield of PCB and 20% of PCR compared with SD, respectively. Therefore, RE would be more effective and suitable for enriching volatile oils from plants or herbs in which volatile oils are water-soluble and with low-content. GC–MS analysis of the products indicates that most compounds in volatile oils of PCB and PCR prepared by SD and RE methods (techniques) are the same, and the percentage contents of the most common compounds change little. Therefore, the quality features of volatile oils extracted by RE are similar to those produced by SD. So RE is not only a way to prepare samples for the aim of volatile oils’ quality analysis but also a good alternative technology in industry for isolating volatile oils from Chinese herbs or other plants.