Soxhlet extraction of solid materials: an outdated technique with a promising innovative future

The applicability of microwave irradiation to the extraction of various types of compounds from soil, seeds, foods and feeds as a novel sample preparation method for chromatography was investigated. Samples were ground and mixed with an appropriate solvent, methanol or methanol-water for polar compounds and hexane for non-polar compounds. The suspensions were irradiated for 30 s, but they were not allowed to boil. After cooling, the irradiation was repeated several times. The samples were then centrifuged, and aliquots of the supernatant were injected into a chromatographic column. The yields of the extracted compounds obtained by microwave irradiation were compared with those obtained by the traditional Soxhlet or shake-flask extraction methods. The microwave extraction method was more effective than the conventional methods. Due to the considerable savings in time and energy, this novel method is suitable for fast extractions of large sample series.