Solid phase microextraction

  Solid phase microextraction, or SPME, is a sample preparation technique used both in the laboratory and on-site. Developed in the early 1990s at the University of Waterloo by Dr. Pawliszyn's group, it is a simple and inexpensive technique where the use of solvents is not necessary.

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SPME can be thought of as a very short gas chromatography column turned inside out. SPME is a fibre coated with an extracting phase, that can be a liquid (polymer) or a solid (sorbent), which extracts different kinds of analytes, from volatile to non-volatile, from different kinds of means, that can be in liquid or gas phase. The quantity of analyte extracted by the fibre is proportional to its concentration in the sample, as long as equilibrium is reached or, in case of short time pre-equilibrium, with help of convection or agitation. After extraction, SPME fibre is transferred to the injection port of separating instruments, like a Gas Chromatograph, where desorption of the analyte takes place and analysis is carried out.

The attraction of SPME is that the extraction is fast and simple and can be done without solvents, and detection limits can reach parts per trillion (ppt) levels for certain compounds. SPME also has great potential field applications: onsite sampling can be done even by nonscientists without the need to have a GC-MS at each location. When properly stored, samples can be analyzed days later in the laboratory without significant loss of volatiles.

Books

• Pawliszyn J.: Solid Phase Microextraction: theory and practice, Wiley-VCH, 1997
• Pawlisyzn J.: Applications of Solid Phase Microextraction, Royal Society of Chemistry, 1999.