Traditional methods of sample preparation for organic analytes, such as Soxhlet extraction and sonication, are both timeconsuming and create large amounts of solvent waste. Typical extractions take up to 6 h to complete, and use well over 100 ml of chlorinated organic solvent. Although newly developed supercritical fluid extraction (SFE) has enjoyed much success owing to its organic solvent-free extraction using non-toxic CO2 as the supercritical solvent, its extraction results depend not only on the solute, but also on the sample matrix. Moreover, more polar hazardous fluids are often required to combine with the organic modifiers to effect complete extraction. In many analytical laboratories, the microwave-assisted dissolution technique is already the method of choice for sample preparation. Other microwave-assisted techniques for sample preparation are being constantly developed and put into practice. The application of microwave energy for the isolation of organic analytes from diverse samples began in the mideighties, and has made great progress with the advent of commercial microwave systems. 1 Compared with the traditional sample preparation methods, microwave-assisted extraction (MAE) is rapid (generally 5 -10 min), solvent saving (generally 20 -30 ml of non-chlorinated organic solvent.) and efficient.Recently, we have developed a series of microwave-assisted techniques for sample pretreatment prior to GC, GC-MS or HPLC determination of target organic analytes in diverse samples. The microwave-assisted experiments were performed with a 600 W microwave sample preparation system (Model MK-1, Xin-Ke Institute of Applied Microwave Technology, Shanghai, China). The operating conditions could be optimized by mainly adjusting three parameters, namely, the magnetron power output, usually set at 100%, the irradiation time (or heating time) and the controlled pressure value. The pressure in the vessel could be indicated by a special-designed optical fiber sensor. There were eight separate stages for pressure selection, and a pressure as high as 4 MPa could be attained. The volume of the PTFE lined digestion vessel was about 60 ml. The turntable could hold nine vessels simultaneously.GC determinations of PAHs, PCBs and triazines were performed on a HP-5 column (0.25 mm, 0.25 µm phase thickness) using a Hewlett-Packard 4890D series gas chromatograph equipped with an electron-capture detector (ECD), a nitrogen phosphorus detector (NPD) and a split/splitless injector operated in the splitless mode. The chromatograph data were obtained and processed in a HP Chemstation (G2070AA, A.04.01).A HP6890 series gas chromatography interfaced to a HP 5973 mass-selective detector with a HP MS Chemstation data system (G1701AA, B.02.05) was used for MS identification of the GC peaks. The column used was a HP-5Ms cross-linked fusedsilica capillary column (30 m × 0.25 mm, 0.25 µm, phase thickness) coated with 5% phenyl-polymethylsiloxane. The HPLC used for the analyses of triazines was a Shimadzu LC-4A with an SPD-1 UV-VIS detector. ...
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