Deep eutectic solvent modified cobalt ferrite nanoparticles in dispersive solid phase extraction of some heavy metals from milk samples prior to ICP–OES

Abstract

In this work, a new magnetic sorbent (cobalt ferrite nanoparticles modified with choline chloride: p-aminophenol deep eutectic solvent) was synthesized and used in magnetic dispersive solid phase extraction of heavy metals (Zn, Ni, Cu, Pb, Hg, and Cr) before their determination with inductively coupled plasma–optical emission spectrometry. In this method, firstly, the proteins of milk sample were precipitated by using trichloroacetic acid. Then, the magnetic sorbent was added into the clear supernatant phase obtained from pervious step and the mixture was vortexed. After isolating the sorbent particles in the presence of an external magnet, the supernatant phase was discarded and the sorbent was eluted using µL-level of ammonia solution. Finally, the eluent phase was injected into analytical instrument for the quantitative analysis. Under the optimized extraction conditions, satisfactory results including low limits quantification (1.4–2.1 ng mL⁻¹) and detection (0.42–0.63 ng mL⁻¹), high extraction recoveries (66–82%), and good precision with relative standard deviations ≤ 3.2 and 3.9% for intra– and inter day precisions, respectively) were obtained. In the last step, the suggested approach was used to determine the selected analytes in various milk samples.