Graphene/sepiolite mixtures as dispersive solid-phase extraction sorbents for the anaysis of polycyclic aromatic hydrocarbons in wastewater using surfactant aqueous solutions for desorption.

Different graphene/sepiolite (G/Sep) solid mixtures have been prepared and tested as nanometric sorbents for the analysis of polycyclic aromatic hydrocarbons (PAHs) using dispersive solid phase extraction (dSPE) and aqueous solutions of surfactants as environmentally friendly agents for desorption. Quantification of the PAHs was carried out by reversed-phase liquid chromatography (RP-HPLC) with fluorescence detection. The adsorption of four PAHs with increasing number of benzene rings into a G/Sep mixture (2/98, w/w) was investigated. A 100% retention was attained for phenanthrene (Phe), pyrene (Pyr) and benzo(a)pyrene (BaP), while for naphthalene (Nap) the maximum retention was close to 75%. The G/Sep mixtures can be used to remove the PAHs from wastewater. The desorption step was carried out using an aqueous surfactant solution: 100 mM non-ionic polyoxiethylen-23-lauryl eter (Brij L23). Considering the whole extraction process, the highest PAH recoveries (50, 92, 83 and 76% for Nap, Phe, Pyr and BaP, respectively) were obtained using 100 mM Brij L23. The developed method shows very high sensitivity, robustness and precision, as well as low limits of detection and quantification, and has been successfully applied to the analysis of PAHs in wastewater samples.