One-pot synthesis of nickel oxide/nickel ferrite nanocomposite and application to dispersive magnetic solid-phase extraction of zinc(II) ions in water and milk samples

An inorganic magnetic nanocomposite named nickel oxide/nickel ferrite (NiO/NiFe2O4) was synthesized using a one-pot hydrothermal method. After successful synthesis and characterization of the nanocomposite, it was applied as a novel adsorbent for dispersive magnetic solid-phase extraction and pre-concentration of zinc(II) ions followed by flame atomic absorption spectrometric detection. The developed method was validated by exploring the affecting parameters, including the amount of the adsorbent (100 mg), sample volume (150.0 mL), sample pH (6.0), adsorption time (15 min), type and eluent concentration (acetic acid 2.0 M), and desorption time (15 min). In the optimal condition, the calibration graph is linear in the concentration range of 0.3-20.0 ng mL(-1) with a satisfactory determination coefficient of 0.9996. The limit of detection and limit of quantification of the method are 0.04 and 0.13 ng mL(-1), respectively. The precision of the method in the term of intra-day and inter day relative standard deviation with six replicates are 1.5% and 3.5%, respectively. A certified reference sample was analyzed applying the developed method and the results confirmed its high accuracy. The applicability of the method was also assayed by determination of Zn(II) ions in various water and milk samples, and the acceptable relative recovery values (96.0-102.0%) were obtained for the spiked samples.