Simultaneous magnetic solid phase extraction of acidic and basic pesticides using triazine-based polymeric network modified magnetic nanoparticles/graphene oxide nanocomposite in water and food samples

In this work, a triazine-based polymeric network modified magnetic nanoparticles/graphene oxide (TPN/Fe3O4 NPs/GO) nanocomposite was successfully synthesized and used as an effective nanosorbent in simultaneous magnetic solid phase extraction of basic and acidic pesticides from food and water samples by HPLC-UV. Imidacloprid (IMI) and 2,4-dichlorophenoxyacetic acid (2,4-D) were selected as model basic and acidic pesticides, respectively. The synthesized TPN/Fe3O4/GO was characterized by field emission-scanning electron microscopy (FE-SEM), Fourier transform-infrared spectroscopy (FT-IR), vibrating sample magnetometry (VSM) and thermogravimetric analysis (TGA). Some parameters that affect the extraction efficiency such as pH of solution, sorbent amount, salt amount, extraction time, desorption solvent volume and desorption time were optimized by central composite design. However, type of desorption solvent and sample volume were optimized by one variable at a time method. Under optimum conditions, the calibration curve was linear in the range of 0.5-500 mu g L-1 and 5.0-500 mu g L-1 for IMI and 2,4-D, respectively. The limits of detection (LODs) for IMI and 2,4-D were 0.17 and 1.7 mu g L-1, respectively. Also, the limits of quantification (LOQs) for IMI and 2,4-D were 0.5 and 5.0 mu g L-1,respectively. The relative standard deviations (RSDs) were < 8.6% (n = 6). The proposed method was successfully applied for extraction and determination of IMI and 2,4-D in cucumber, tomato and water samples and satisfactory results (recoveries >= 90%) were obtained.