Covalently bonded double-charged ionic liquid on magnetic graphene oxide as a novel, efficient, magnetically separable and reusable sorbent for extraction of heavy metals from medicine capsules

A new, efficient and reusable double-charged ionic liquid modified magnetic graphene oxide (DIL-MGO) was used as a special sorbent in the solid-phase extraction process for simultaneous separation and preconcentration of Pb(II), Cd(II), Ni(II), Cu(II) and Cr(III). The ionic liquid was chemically attached to magnetic graphene oxide nano sheets and then characterized by field emission scanning electron microscopy (FE-SEM), thermo gravimetric analysis (TGA), X-ray diffraction (XRD), vibrating sample magnetometry (VSM) and Fourier transform infra-red spectroscopy (FT-IR). This sorbent employs a hybrid combination of an ionic liquid and graphene oxide extraction properties, which contributed to the increased extraction efficiency via improving mass transfer yield. An ultrasound-assisted double charged ionic liquid-linked magnetic micro solid phase extraction method (US-assisted DIL-MmSPE) coupled with micro sampling atomic absorption spectrometry was utilized for the determination of heavy metals. Effecting parameters, including sample pH, amount of DIL-MGO, extraction time, type and concentration of desorption solvent, were investigated and optimized. Good recoveries and satisfactory relative standard deviations (RSDs) under the optimal conditions were achieved. The limits of detection were from 0.2 to 1.8 mu g L-1. Method performance was investigated by the determination of the mentioned heavy metals in complex medicine capsule matrixes with good recoveries. Finally, the sorbent was reused for eight runs without significant loss of its recovery.