Application of a magnetic graphene nanocomposite for organophosphorus pesticide extraction in environmental water samples.

A novel magnetic nanocomposite was prepared and applied for the extraction of organophosphorus pesticide residue (malathion, chlorpyrifos, isocarbophos, fenamiphos, profenofos) in environmental water by magnetic solid phase extraction. The magnetic nanocomposite was synthesized by coating Fe3O4 with silicon dioxide and then bonding with graphene oxide under the catalytic action of hydrazine hydrate. A residue analysis method for the determination of organophosphorus pesticides in environmental water was established via magnetic solid phase extraction with the nanocomposite as the sorbent, followed by gas chromatography with flame photometric detection (GC-FPD). Various experimental parameters affect extraction efficiency and must be optimized, such as the sorbent amount, the type and volume of desorption solvent, desorption time, desorption step, salt concentration and pH. Under the optimum conditions, a linear response was achieved for malathion and chlorpyrifos in the concentration range of 0.05 mg L-1-5 mg L-1. Other organophosphorus pesticides were quantified in a concentration range of 0.1 mg L-1-5 mg L-1, and the coefficient of correlations were between 0.996 and 1 for this method. The method was used to determine organophosphorus pesticides in river water and groundwater. The average recoveries ranged from 90.2% to 102.9%, with low relative standard deviations (RSD), and the limits of detection (LOD) were between 0.016 mg L-1 to 0.033 mg L-1 at a signal to noise ratio of 3. The method was efficient for the residue analysis of organophosphorus pesticides in water with easy operation, high sensitivity, and good precision.