Surfactant‐Based Materials*
4.5 Final Remarks
Sample preparation is generally necessary for determination of analytes in real samples.
Interestingly, the development of modern sample preparation techniques has been investigated using surfactants as alternative extraction media, both based on liquid‐ and solid‐phase extraction. Surfactants are less toxic and cheaper than the extractants used in conventional LLE. The commonly used surfactants are commercially available and, since it is not necessary to evaporate off the solvents, no analyte is lost during the extraction process. External forces were also applied to accelerate the extraction equi- librium and enhance the extraction yield. Reduction of analysis time and toxic chemical usage can afford some economic and environmental benefits.
In SPE techniques, surfactants have been used to modify the surface of several solid sorbents in order to improve their adsorption capability for the target organic compounds. In addition, the extraction systems were miniaturized to a small scale in which micro volumes of extraction solvent were used. In the case of surfactant‐
coated MNPs, the surfactant can be physisorbed or chemisorbed depending on the nature of the interaction within the surfactant and the nanoparticle. Elution of ana- lytes is also straightforward since hemimicelles/admicelles are easily destroyed in the presence of a low volume of organic solvents. In the case of physisorption, extracts contain high surfactant concentrations that may interfere with mass spec- trometer, UV, or fluorescence detection. In addition, the extracts are incompatible with separation techniques (e.g. HPLC, GC, and CE). However, the use of these tech- niques prior to GC analysis has not been widely developed due to the nature of sur- factants, which are characterized by their high viscosity and low volatility.
Furthermore, direct introduction could clog the injector or column. Additionally, they can adsorb onto the stationary phase, altering the analyte’s interaction with the stationary phase of the GC column. Research in GC analysis after surfactant‐based extraction is still in progress and, hopefully in the near future, the application of these methods will be developed for GC analysis.
It is clear that surfactant‐based materials were mostly used in sample preparation techniques for liquid samples. From this perspective, application of surfactant‐based materials for direct extraction of the target analytes from solid‐state samples using solid–liquid or solid–solid extraction is of interest in further studies. In addition, the synthesis of novel surfactants with specific functional groups could be useful for the development of more selective extraction procedures via possible selective interactions, i.e. the use of surfactants for enantiomeric enrichment, enrichment of ultratrace target analytes from high matrix samples, and also application of new surfactants in separa- tion techniques. In the area of analytical method development there is a continuing trend towards the development of new methodologies for obtaining both better selec- tivity and sensitivity. Automation of new surfactant‐based microextraction techniques is also attracting increasing interest.
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