Solid-phase microextraction (SPME) is a sample preparation technique that use fibre coated with extracting phase that extract different kinds of analytes for different fibre coating. This is solventless techniques for the isolation of organic compounds (analytes) in the form of liquid and gaseous either it volatile or not. The SPME apparatus is very simple device that consisting a fibre holder and a fibre assembly with built-in fibre (1 to 2 cm long) inside the needle which looks like a modified syringe. Moreover, SPME fibre is a thin fused-silica optical fibre, coated with a thin polymer film such as polydimethylsiloxane (PDMS).
After equilibration takes place, the SPME fibre is inserted into the hot injector of a gas chromatograph to volatilize the analytes. The analytes that were adsorbed to the fibre from the sample headspace are desorbed directly in the GC inlet analysis. By matching fibre polarity with target analyte characteristics, the analysis can be optimized to improves sensitivity and performance.
The factors that affect the SPME performance are the coating material, thickness of fibre, sample agitation, sample pH, salt addition and the extraction procedure. Fibre SPME can be performed in three basic modes such as direct extraction, in a headspace configuration, and in a membrane-protected approached. When the fibre is only in contact with the gas phase of a sample in a closed vial, there is a three-phases (at least) partitioning between the fibre, the headspace and the sample.