Graphene oxide dispersed with ferrite nano - particles as magnetic solid phase extraction adsorbent for chlorpyrifos and diazinon

Magnetic graphene oxide, Fe3O4-GO has been synthesized through oxidation of graphite via modified Hummer’s method followed by a one step co-precipitation method. Fe3O4-GO was used in the extraction of two organophosphorus pesticides (OPPs), namely chlorpyrifos and diazinon using magnetic solid phase extraction (MSPE) technique. The GO and Fe3O4-GO synthesised was characterized using Fourier transform infrared spectroscopy (FT-IR), and field emission scanning electron microscopy (FESEM). Optimum conditions obtained from the optimization process were as follows: 80 mL sample volume, 50 mg of adsorbent, 10 min extraction time followed by desorption process using 500 µL of acetonitrile. Under the optimum conditions, Fe3O4-GO MSPE method showed excellent linearity in the range of 0.1-10 µg L-1 with coefficient of determination (R2) of 0.9997 for both OPPs. Precision studies found that the repeatability of this Fe3O4-GO MSPE method (RSD, n = 3) were 9.95% and 9.05% for chlorpyrifos and diazinon respectively. Meanwhile the reproducibility (RSD, n = 9) observed was 11.45% for chlorpyrifos and 13.35% for diazinon. The limit of detection (LOD = 3 S/N) for chlorpyrifos was 0.034 µg L-1 and 0.40 µg L-1 for diazinon. Lake water sample was spiked with 0.5 µg L-1 of each of the OPPs after confirming the non-detection in the sample using gas chromatography-electron capture detector (GC-ECD). Percentage recoveries of the two OPPs from lake water samples were found to be 57.71% for chlorpyrifos and 73.86% for diazinon. The Fe3O4-GO MSPE method was found to be susceptible to matrix effect from the lake water sample analysed. The Fe3O4-GO MSPE method was also applied to the determination of the two OPPs from tomato sample using matrix-matched calibration curve in the range of 1-50 µg L-1. Good coefficient of determination (R2) value of 0.9963 and 0.9897 for chlorpyrifos and diazinon respectively was observed. Both OPPs were found to be present in the tomato sample analysed (0.19 µg L-1 of chlorpyrifos and 7.88 µg L-1 of diazinon