In this research, we report the synthesis and functionalization of magnetic iron nanoparticles using green chemistry (olive oil) for application of dispersive solid-liquid phase microextraction (DSLME) as a novel method for preconcentration and determination of nickel ions in soil, potato, red tea, white tea, mushroom, lettuce, cabbage, apple, urban water, purified drinking water through household water treatment device. Nickel is a dangerous toxic metal that can cause serious damage to the environment and then its removal is necessary. Recently, iron oxide nano materials have gained much attention due to their properties, such as extremely small, non-toxic, excellent magnetic properties, high surface area, great biocompatibility and high level of reactivity with metal which makes them worthwhile in the removal of these metals. For optimizing the important parameters affecting the extraction procedure, analyte concentration, pH, type of disperser solvent, absorption time, ionic strength effect, type of desorption solvent and desorption time investigated. SEM and FT-IR spectrum used for characterization of the synthesized magnetic nanoparticles. The measurements were done under the optimized conditions. Matrices effect and accuracy were examined by the determination of the relative recovery (RR%) of the real samples. Linear range, detection limit and relative standard deviation (RSD) are 1-5000 ng/ml, 0.821 ng/ml and 0.196%, respectively. (C) 2016 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.