Solid phase microextraction SPME

This article is aimed at analysts concerned with the pre-concentration of compounds, usually in trace quantities, in complex matrices. Traditional methods are time-consuming, require large sample volumes and large quantities of high-purity solvent, or are liable to extract impurities that can increase the background noise of measuring equipment. Solid phase microextraction (SPME) is a solvent-free extraction method that does not have these drawbacks. Compounds are extracted by adsorption onto the coating of a fiber or capillary. This process does not involve total extraction of the compound, but rather its equilibrium between the matrix and the fiber coating. Under certain conditions, there is a relationship between the quantity of substance adsorbed on the coating and its concentration in the sample (or matrix) if the latter has undergone pre-transformation.) The most widely used coating is PDMS (polydimethylsiloxane), but new polymers (polypyrrole, crown vinyl ethers and molecularly imprinted polymers) have broadened the range of applications. The choice of extraction mode - immersion in the sample or in its headspace - influences exchange kinetics. Extraction yields depend on sample volume, pH, ionic strength, equilibrium constant, temperature and agitation. Coupling SPME with chromatographic, electrophoretic and mass spectrometric techniques enables the process to be used quantitatively. This article explains the principle of the method and provides information on how to implement it, before moving on to applications such as the determination of organic contaminants in soil, air or water, and the detection of pesticides in food. But also the determination of drug substances in biological matrices. Metabolomic studies, or the search for metabolites to assess the impact of toxic substances on organisms, are also covered.

A glossary at the end of the article lists definitions that are important or useful for understanding the text.