Preparation of a magnetic graphene/polydopamine nanocomposite for magnetic dispersive solid-phase extraction of benzoylurea insecticides in environmental water samples

Abstract

A magnetic graphene/polydopamine (MG/PDA) nanocomposite has been prepared and used as sorbent for magnetic dispersive solid-phase extraction (MDSPE) of four benzoylurea insecticides in environmental water samples. The obtained nanocomposites were characterized by transmission electron microscopy, scanning electron microscopy, vibrating sample magnetometry, powder X-ray diffraction, fourier transform infrared spectroscopy, surface area and porosity analysis and thermogravimetric analysis. To investigate the adsorption performance of MG/PDA for target analytes, various parameters affecting the MG/PDA-based MDSPE procedure were optimized. Under the optimal conditions, the established method exhibits good linearity (R² ≥ 0.9988) in the concentration range 2.5-500 µg L^-1. A low limit of detection (0.75 µg L^-1, signal/noise = 3:1), a low limit of quantification (2.50 µg L^-1, signal/noise = 10:1), and good precision (intraday relative standard deviation ≤3.6%, interday relative standard deviation ≤4.5%) are also achieved. Finally, the simple, fast, and sensitive sample preparation technique was successfully used to determine benzoylurea insecticides in environmental water samples.

Figure 1

Schematic diagram of the MDSPE procedure with the MG/PDA composite.

Figure 2

TEM images of (A) Fe₃O₄ and (B) MG. (C) SEM image of MG/PDA.

Figure 3

(A) Magnetic curves of the prepared materials. (B) XRD patterns of (a) Fe₃O₄, (b) MG, (c) MG/PDA and (d) MG/PDA treated with the developed MDSPE method. (C) FT-IR spectra of the prepared materials. (D) N₂ adsorption–desorption isotherms of MG/PDA.

Figure 4

TGA curves of MG/PDA and (a) treated with the developed MDSPE method.

Figure 5

Effect of different parameters on the extraction efficiency of BUIs from water: (A) amount of adsorbent, (B) extraction time, (C) salt concentration, (D) desorption solvent, (E) desorption solvent volume, and (F) desorption time.

Figure 6

Regeneration and reusability of MG/PDA.

Figure 7

Typical chromatograms of blank (a) and spiked water (b) 100 μg L⁻¹; (c) 250 μg L⁻¹) samples from the upper reach of the Tiantang River on the Nangezhuang Enterprise Park.