Materials modified with ionic liquids for solid phase extraction

By R. Lucena -
The application of ionic liquids (ILs) in the analytical chemistry context has been increased in the last years due to their exceptional chemical and physical properties. The term IL is used to define a broad class of semi-organic salts composed entirely by ions which are liquids in the range of 180-600K. Among all these potential substances, room-temperature ILs (defined as the ILs which present a melting point lower than 100 ºC) are specially interesting due to their easy manipulation at normal experimental conditions. Among the main properties of these special solvents, their negligible vapor pressure, their good thermal stability and good extractability towards a variety of analytes should be highlighted. Since ILs can be obtained as a combination of different cations and anions, the researcher can select the more appropriate IL to solve a given analytical problem. This tunable nature makes them "task-specific" solvents.

ILs have been used as solvents in (micro)extraction techniques including classic (liquid-liquid extraction) and modern (single drop microextraction, dispersive liquid-liquid microextraction) approaches. Moreover, polymeric ionic liquids have been proposed as sorptive phases in solid phase microextraction. However, the use of IL in solid phase extraction is scarce referenced in the literature. The required covalent immobilization of the ILs in the surface of an inert support can be the reason for this fact. In a recent article published in Analytica Chimica Acta, L. Vidal, M-L Riekkola and A. Canals reviewed the scientific articles devoted to ILs-modified materials.


ILs miss their liquid nature when are immobilized in a solid support but they maintain some of their exceptional properties (e.g: thermal stability or extraction capacity). Moreover, their covalent bond to the inert support avoids the final elution of the IL which may be problematic when gas chromatography (due to the non-volatility of ILs) or liquid chromatography (since in most cases the ILs should be diluted in a organic solvent) are finally employed for the analytes determination. Therefore, ILs-modified materials are promising sorbents and they can be also employed as stationary phases in liquid chromatography. For further details, the readers are referred to the mentioned article.

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