Synthesis and characterization of Fe₃O₄@Al₂O₃-1- (2-pyridylazo)-2-naphthol for preconcentration of trace metals in fuel oils prior to inductively coupled plasma-optical emission spectroscopy analysis

A magnetic spherical nanocomposite Fe₃O₄@Al₂O₃-1-(2-pyridylazo)-2-naphthol (PAN) was synthesized by using co-precipitation method and used for preconcentration of metals from fuel oils for the first time. Sample analysis was done using inductively coupled plasma-optical emission spectroscopy (ICP-OES). The synthesized adsorbent was characterized by Fourier transform–infrared spectroscopy (FT–IR), Scanning electron microscope with energy dispersive X-ray spectroscopy (SEM-EDX), Powder X-ray diffraction (P-XRD) and Transmission electron microscopy (TEM). The latter confirms the particle size range of 37–74 nm. Minitab18 statistical software was used for experimental design to obtain the most optimum extraction conditions. The optimum condition for the factors affecting extraction efficiency were pH 6.5, 40 mg adsorbent mass, 1 mol/L eluent concentration, 20 µg/g model oil concentration and 35 min sonication time. The optimum parameters were then applied for extraction of Co, Cr, Cu, Mn, Mo, Pb, Ti and V in selected petroleum samples. The developed m-SPE demonstrated accepted accuracy (86–96%), precision (0.9–4.8%) and low method detection limits (0.11–0.62 µg/g) under optimum conditions. Preconcentration factors of 168, 166, 152, 165, 164, 150, 160, and 150 for Co, Cr, Cu, Mn, Mo, Pb, Ti and V, respectively, were obtained. The enrichment factors for Co, Cr, Cu, Mn, Mo, Pb, Ti, and V, respectively, were 30, 24, 11, 20, 26, 10, 18, and 8. The optimized and validated m-SPE method was applied in real fuel oil samples. In the fuel oils, Cr reported higher concentrations up to 8.99 µg/g while Mn showed the lowest concentrations of less than 0.2 µg/g.