Modification of Magnetic Graphene Oxide by an Earth-Friendly Deep Eutectic Solvent to Preconcentrate Ultratrac Amounts of Pb(II) and Cd(II) in Legume Samples

A novel magnetic solid-phase extraction adsorbent using deep eutectic solvent-coated magnetic graphene oxide (EgLiCl-mGO) was proposed for simultaneous preconcentration of Pb(II) and Cd(II). The nanocomposite was characterized by Fourier Transform Infrared Spectroscopy, X-ray diffractometry, and alternative gradient force magnetometer. Parameters that could affect the preconcentration recoveries of the target ions were investigated via the one-factor-at-a-time method. The optimum conditions are pH of 4 ± 0.5, EgLiCl-mGO amount of 1.0 × 10−2 g, adsorption time of 5 min, eluent of HNO3 (1 mL, 2 mol L−1), and desorption time of one minute. The swelling property of the adsorbent versus pH was studied. The linearity of the dynamic range for Pb(II) (5.0 × 10−6–4.0 × 10−4 g L−1) and Cd(II) (5.0 × 10−6–15 × 10−5 g L−1) was recorded. The limits of detection were Pb(II): 1.2 × 10−6 g L−1 and Cd(II): 47 × 10−8 g L−1. The preconcentration factor of 50 was calculated for both ions and the relative standard deviations were 1.27% for Pb(II) and 0.94% for Cd(II). Reusability, effect of interference ions, selectivity, isotherm adsorption, kinetic adsorption, and thermodynamic adsorption were established. The adsorbent was successful at preconcentrating the ions in legumes.