Solvent-free micro extraction technique

The solvent-free micro extraction technique SPME is an important step towards the instrumentation and automation of the SPE technique for online sample preparation and introduction to GC-MS (Zhang et al., 1994 Eisert and Pawliszyn, 1997 Lord and Pawliszyn, 1998). It involves exposing a fused silica fibre coated with a liquid polymeric material to a sample containing the analyte. As an extraction and enrichment technique it compares to P T methods (MacGillivray et al., 1994). Also derviatization steps can be coupled to the extraction process for polar compounds and improved efficiencies (Pan et al., 1997). The typical dimensions of the active fibre surface are 1 cm X100 pm. 

Another possibility for essential oils extraction is the use of microwave-assisted extraction (MAE). This methodology appeared to be quite attractive for the isolation of essential oils. The main advantage of using MAE for essential oils extraction is the effective heat transfer that allows quicker times of extraction as compared to classical methods. In the last few years, different applications using microwave energy have been developed. A recent modification of this technique is solvent-free microwave extraction (SEME), where the sample is placed in the reactor inside the microwave oven without any solvent.A cooling system outside the micro-wave oven cool the extract continuously. Einally, the mixrnre of water and essential oil is collected and separated in a vessel. 

During the last few years, miniaturization has become a dominant trend in the analysis of low-level contaminants in food and environmental samples. This has resulted in a significant reduction in the volume of hazardous and expensive solvents. Typical examples of miniaturization in sample preparation techniques are micro liquid/liquid extractions (in-vial) and solvent-free techniques such as solid-phase microextraction (SPME). Combined with state-of-the-art analytical instrumentation, this trend has resulted in faster analyses, higher sample throughputs and lower solvent consumption, whilst maintaining or even increasing assay sensitivity. 

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