Development of dynamic microwave and sonication-assisted extraction techniques coupled on-line to gas chromatography
Abstract: This thesis describes the evaluation and construction of two solvent extraction methods for solid samples. The techniques are called Dynamic microwaveassisted extraction (I-III) and Dynamic sonication-assisted solvent extraction (IV-V). Both techniques are based on dynamic solvent extraction and are performed at elevated temperatures and pressures. These characteristics enhance the extraction rates and allow solvent consumption to be reduced. In addition, due to the enhanced extraction, less hazardous extraction solvents than those used for the reference methods can be utilized. The developed techniques were validated in a comparative study with established extraction methods, such as Soxhlet, static microwave-assisted extraction and static sonication-assisted extraction. The results obtained from the presented techniques were in all cases found to be better or equal to the established reference methods in terms of extraction recovery, time and precision. The microwave-based technique was coupled to a solid phase extraction system (II). This allowed extraction, trapping and purification of analytes from complex samples such as soil and sediment to be done in a single, automated analytical procedure. Both developed methods were also connected on-line to large-volume injection gas chromatography (III, V). Thus automation of the entire laboratory procedure was achieved. The introduced methods were used for the determination of polycyclic aromatic hydrocarbons in sediment and soil (I, II) and organophosphate esters in samples of indoor air collected on glass fiber filters (III-V).
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