Salt-induced ionic liquid-based microextraction using a low cytotoxic guanidinium ionic liquid and liquid chromatography with fluorescence detection to determine monohydroxylated polycyclic aromatic hydrocarbons in urine.

A novel ionic liquid (IL)-based microextraction method has been developed for the determination of four hydroxylated polycyclic aromatic hydrocarbons (OHPAHs) in urine samples. The water soluble IL-based surfactant selected as extraction solvent is decylguanidinium chloride (CGu-Cl), the cytotoxicity and micellar behavior of which were evaluated. The proposed salt-induced IL-based preconcentration method simply consists in adding NaClO to the aqueous medium containing the IL to promote its water insolubility. The entire method was optimized, requiring the use of only 20 μL of CGu-Cl for 10 mL of diluted urine sample (1:10) without any pH adjustment, followed by the addition of NaClO to ensure a 5% (w/v) content. A cloudy solution was observed immediately, and after the application of 4 min of vortex and 8 min of centrifugation, the droplet was diluted up to 60 μL with a mixture of acetonitrile:water (30:70) and injected into the liquid chromatograph with fluorescence detection. The method was validated using both synthetic urine and human urine as matrix for the determination of the four OHPAHs. The following analytical features were obtained: detection limits down to 1 ng·L in real urine; inter-day reproducibility (as RSD in %) always lower than 17% when dealing with real urine samples spiked at 80 ng·L; and average relative recoveries of 102% in real urine samples at such low spiked levels. Despite the simplicity of the proposed method, it performed successfully with complex urine samples. Graphical abstract Salt-induced IL-based microextraction using a low cytotoxic IL for mono-OHPAHs in urine.