Solvent-assisted dispersive liquid-solid phase extraction of organophosphorus pesticides using a polypyrrole thin film-coated porous composite magnetic sorbent prior to their determination with GC-MS/MS.

A porous composite magnetic sorbent was developed and used as a solid phase for the solvent-assisted preconcentration of organophosphorus pesticides. The hierarchical porous composite sorbent was composed of polypyrrole thin film coated on the surface of porous alginate beads with embedded magnetite nanoparticles. The pores in the alginate hydrogel beads were produced by carbon dioxide bubbles from the reaction of incorporated calcium carbonate with hydrochloric acid. The porous network was filled with dichloromethane to assist extraction. The fabricated porous composite sorbent was characterized and sorbent fabrication and extraction conditions were optimized to obtain the best extraction performance. The developed sorbent was coupled with GC-MS/MS to determine organophosphorus pesticides in fruit juices and vegetable. Under optimized condition, the developed method provided good linear range of 0.03-200 μg L-1 for dichlorvos, malathion, and fenthion, and 0.075-200 μg L-1 for mevinphos, dimethoate, and parathion methyl, respectively. Limits of detection were in the range 0.010 to 0.025 μg L-1. This method exhibited good relative recoveries in the range 84 to 99% and RSDs lower than 8%. The good stability of the sorbent enabled up to eight cycles of reuse.Graphical abstract.