Recent Extraction Techniques with Emphasis on Supercritical Fluid Extraction and Microwave-assisted Extraction
Sammanfattning: Today’s requirements of fast, reliable and selective analytical methods with minimal usage of organic solvents have accelerated the development of new, automated extraction techniques. In this thesis recent extraction techniques with emphasis on supercritical fluid extraction (SFE) and microwave-assisted extraction (MAE) were investigated. Different environmental and industrial applications such as extraction of pesticides from process dust, active compounds in pharmaceutical tablets, mycotoxins in cereals and aromatic amines released from azo dyes in leather have been studied to outline advantages and limitations of the techniques. In all cases the extraction efficiencies were similar or better, solvent usage reduced and extraction times shortened compared to traditional extraction techniques such as sonication and liquid-solid extraction (shaking) procedures. Even though recent extraction techniques in most cases are superior to the conventional techniques, they differ in terms of selectivity, simplicity and sample throughput as discussed in this thesis. By utilizing an elongated trap in SFE further selectivity in the collection step was achieved for extractions of aromatic amines and for separation of fat-soluble vitamins from lipids. Devices to perform direct SFE of liquid samples were tested, resulting in a selective extraction of alkylphenols from real waste water samples. Furthermore, a fractionated MAE procedure including a reaction/extraction step was developed for the determination of amines after reductive cleavage of azo dyes in leather. A variant of pressurized liquid extraction (PLE) that utilizes water as extracting media is pressurized hot water extraction (PHWE). This technique was investigated for extraction of pesticides from process dust and obtained results were compared with results obtained using SFE. With better understanding of the characteristics of the recent techniques, conventional techniques can in most cases be replaced. In the future it is anticipated that combinations of different extraction techniques will appear in a single analytical method, where the inherent advantages of each technique are utilized. This was here demonstrated , where leather samples were degreased using SFE and further treated using MAE.
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