Magnetic Solid-Phase Microextraction for Lead Detection in Aqueous Samples Using Magnetite Nanoparticles

A magnetic solid-phase microextraction procedure was developed to detect lead in aqueous samples by flame atomic absorption spectrometry (FAAS). Fe3O4 nanoparticles were synthesized by coprecipitation and the crystalline phase was confirmed by X-ray diffraction. The point of zero charge (PZC) indicated that the oxide surface was negatively charged at pH levels above 9.4. pH 9.0 is the best for adsorption and the influence of stirring time and adsorbent mass were analyzed and set at 4 min and 3.0 mg, respectively. The best desorption conditions were obtained for 500 µL of 0.5 mol L-1 HNO3 as eluant. The limit of quantification (LOQ) and relative standard deviation (RSD) were 16.48 µg L-1 and 0.25%, respectively. The linear range was found to be 16.48‑500 µg L-1. The accuracy was evaluated by recovery tests in mineral water, micellar water and aqueous makeup remover samples, showing values in the range of 95.94 to 118%.