A novel in situ preconcentration method with ionic liquid-based surfactants resulting in enhanced sensitivity for the extraction of polycyclic aromatic hydrocarbons from toasted cereals

A preconcentration procedure utilizing IL-based surfactants it is described for the first time. The procedure is based on transforming a water-soluble IL-based surfactant, 1-hexadecyl-3-butylimidazolium bromide (C16C4Im-Br), into a water-insoluble IL, 1-hexadecyl-3-butylimidazolium bis[(trifluoromethane)sulfonyl]imide (C16C4Im-NTf2), via a simple metathesis reaction. The preconcentration procedure is used in combination with a micellar microwave-assisted extraction (MMAE) method for the analysis of sixteen polycyclic aromatic hydrocarbons (PAHs) from toasted cereals. The obtained microdroplet of C16C4Im-NTf2 containing the extracted PAHs is then diluted with acetonitrile and injected into a high-performance liquid chromatograph (HPLC) employing UV–vis and fluorescence detection. This in situ preconcentration step highly improves the sensitivity of the MMAE despite the complexity of the solid matrix. The developed in situ preconcentration method exhibited almost quantitative extraction efficiencies (80–95% in average) for the PAHs studied, and good precision values (lower than 14%). The overall MMAE + in situ preconcentration method presented limits of detection down to 0.03 μg kg−1.

► An in situ preconcentration procedure is developed for ionic liquid (IL)-based surfactants. ► This method highly improves the sensitivity of extractions for complex solid samples with IL-based surfactants. ► The combined extraction/preconcentration with IL-based surfactants is organic solvent free. ► The optimized method for the 16 EU PAHs in cereals reached detection limits down to 0.03 μg kg−1.