Ultrasound-Microwave Hybrid-Assisted Extraction Coupled to Headspace Solid-Phase Microextraction for Fast Analysis of Essential Oil in Dry Traditional Chinese Medicine by GC–MS

A novel one-step sample preparation technique termed ultrasound-microwave hybrid-assisted extraction coupled to headspace solid-phase microextraction (UMHE-HS-SPME) was developed in this study, which was used for the determination of essential oils in dry traditional Chinese medicine (TCM) based on gas chromatography–mass spectrometry. The dry roots of Angelica dahurica were used as the model TCM. In this work, ultrasound-assisted extraction was first combined with microwave-assisted extraction coupled to headspace solid-phase microextraction and applied to the rapid determination of A. dahurica. Sample preparations including isolation, extraction, and concentration of essential oils were performed in a single step. The effects of various parameters including fiber coating, ultrasound power, and irradiation time were investigated thoroughly and optimized. To further demonstrate the method’s feasibility, the conventional steam distillation (SD) method was used for the analysis of essential oils in the TCM to compare with the proposed method. The results show that more essential oil compounds were isolated and identified by UMHE-HS-SPME than by SD. Moreover, compounds with higher boiling point and many more oxygenated compounds were extracted from A. dahurica by the proposed method. In addition, the SD method required a long time (6 h) to isolate the essential oils, and large amounts of organic solvent for further extraction, while UMHE-HS-SPME needed only 10 min to prepare the samples, and no organic solvent. Relative standard deviation values less than 10 % show that the present method has good precision. According to the experimental results, the advantages of the proposed method are: short extraction time, high extraction efficiency, and solvent-free extraction. Thus, UMHE-HS-SPME is an alternative tool for fast analysis of essential oils in dry TCMs and can be potentially extended to other target analytes in dry matrix.