Ultrasonic Nebulisation Extraction: Extraction Column Coupled with Liquid Phase Microextraction for Analysis of the Volatile Organic Compounds in Foeniculum vulgare Mill. as a Model

Introduction As the concentrations of the volatile organic compounds are always low and their matrix is complex, it is necessary to pre-concentrate the volatile organic compounds before analysis. Ultrasonic nebulisation extraction with a self-made extraction column coupled with liquid phase microextraction is developed for the extraction of active constituents from spices. Objective To develop an environmentally compatible extraction technique for the preparation and analysis of the volatile organic compounds from spices. Method The sample is placed into the nebulisation vessel of a nebulisation humidifier and a purging gas is blown through the vessel continuously. When the nebuliser is switched on, a ultrasonic fountain is formed by ultrasonic vibration and the target analytes are transferred from the sample solution to the vapour phase and then concentrated on the extraction solvent in the extraction column. After extraction for 3 min and allowed to stand upright for 5 min, the extract is analysed by GC and GC–MS. Different methods of comparison can then be carried out. Results Optimum conditions were found to be: 30 μL of n-tetradecane as the extraction solvent, a flow rate for the purging gas of 40 mL/min, a purging time of 3 min and a standing time was 5 min. The contents of constituents in the extract obtained by the proposed method were close to those obtained by hydrodistillation (HD). Moreover, the proposed method achieves higher enrichment efficiency. Conclusion A method was developed for the extraction of volatile organic compounds from spices. The study has shown that it is a fast and environmentally sustainable technique. Copyright © 2012 John Wiley & Sons, Ltd.