Dispersive microextraction based on magnetic polypyrrole nanowires for the fast determination of pesticide residues in beverage and environmental water samples

In this study, magnetic polypyrrole nanowires (mPPYs) were fabricated via a simple co-mixing method based on an "aggregation-wrap" mechanism. The polypyrrole (PPy) nanowires were synthesized by in situ chemical oxidative polymerization using cetyltrimethylammonium bromide as the "soft template" and the magnetic nanoparticles (MNPs) prepared using solvothermal methods. Typically, when these two nanomaterials were vortically mixed in a solvent, the MNPs were wrapped into the PPy nanowire networks that formed during the aggregation process, leading to the formation of mPPYs which can be separated from the solvent rapidly and conveniently by a magnet. Due to the better permeability, good adsorption ability, and magnetic separability of the resultant material, mPPYs were applied for the enrichment of 11 pesticides including organophosphorus, organochlorine, and pyrethroid using magnetic solid phase extraction (MSPE) to test their feasibility in sample preparation. Several parameters affecting the extraction efficiency were investigated, and under the optimized conditions, a simple and effective method for the determination of pesticide residues was established by coupling with gas chromatography/mass spectrometry (GC/MS) analysis. The whole pretreatment process was rapid and can be accomplished within 15 min. The linearity range of the proposed method was 0.2-10 mu g/L, with correlation coefficients (R) of 0.995-0.999; the limits of quantification for the target compounds were in the range of 0.09-0.29 mu g/L. In addition, an acceptable reproducibility was achieved by evaluating the intra- and inter-day precisions with relative standard deviations of less than 14 and 16 %, respectively. Finally, the established MSPE-GC/MS method was successfully applied for the determination of pesticide residues in beverage teas, juices, and environmental water samples.