Selective microextraction of polycyclic aromatic hydrocarbons using a hydrophobic deep eutectic solvent composed with an iron oxide-based nanoferrofluid

A simple and fast method is described for the extraction of polycyclic aromatic hydrocarbons (PAHs) from complex samples. It is based on the use of a nanoferrofluid modified with a ternary hydrophobic deep eutectic solvent. A predictive model was used for the selection of the optimal eutectic mixture. The entire microextraction only takes a few minutes for completion. Under the optimal extraction conditions (by using menthol, borneol and camphor in a molar ratio of 5:1:4; 80 mg of nanoferrofluid), it offers marked improvements in terms of selectivity and sensitivity. The limits of detection range between 0.31 and 5.9 ng·L^-1, and recoveries from spiked samples between 91.3 and 121%. In addition, the strong interactions between PAHs and the extractant were supported by quantum mechanical calculations. This results in a better insight into the microextraction mechanism, providing a fast, environmentally friendly and effective route for the optimization of pretreatment parameters. The method was successfully applied to the determination of the PAHs naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, chrysene, benzo[b]fluoranthene, benzo[a]pyrene, dibenzo[a,h]anthracene, benzo[g,h,i]perylene and indeno[1,2,3-c,d]pyrene in 12 kinds of coffee samples after different roasting conditions. Graphical abstract Schematic presentation of nanoferrofluid modified with ternary hydrophobic deep eutectic solvent and their application for selective microextraction of ultra-trace polycyclic aromatic hydrocarbons in coffee prior to HPLC analysis.