Magnetic solid-phase extraction of organophosphorus pesticides from fruit juices using NiFe2O4@polydopamine@Mg/Al-layered double hydroxides nanocomposites as an adsorbent

Herein, we developed a novel three-layer nanocomposite for adsorption/extraction of organophosphorus pesticides in fruit juice samples. This magnetic nanocomposite was fabricated by coating polydopamine and Mg/Al layered double hydroxides onto NiFe2O4 nanoparticles, which overcomes the shortcomings of low surface area and easy agglomeration associated with conventional Fe-based crystal nanoparticles. Additionally, the higher dispersibility of polydopamine and larger specific surface area of Mg/Al layered double hydroxides are conducive to rapid dispersion and efficient adsorption of organophosphorus pesticides by the synthesized nanocomposites, thereby greatly improving the efficiency of magnetic solid-phase extraction. The extraction method based on as-synthesized nanocomposites provided average extraction recoveries of 84.9% for methamidophos, parathion and phoxim, an increase of ca. 30% and 19% over those of NiFe2O4 and NiFe2O4@polydopamine, respectively. The main operational parameters were firstly screened and then optimized using Plackett-Burman and central-composite design, respectively. Under optimized conditions, this proposed method yielded low detection limits (0.06-0.13 mu g L-1) and high intra- and inter-day precisions (2.7-4.5%). Average extraction recoveries for organophosphorus pesticides were 81.8-94.4% in grape, apple, orange, peach and mango fruit juices. To sum up, it integrates highly efficient preconcentration/extraction/dispersion, as well as rapid separation/collection into one synchronous step, satisfies the technical requirement of modern analytical pretreatment and thus enriches the multi-functional application of Fe-based nanoparticles.