Magnetic molecularly imprinted nanoparticles based on grafting polymerization for selective detection of 4-nitrophenol in aqueous samples

In this study, an analytical procedure for the selective extraction and detection of 4-nitrophenol (4-NP) was investigated by using of molecularly imprinted polymer on the surface of magnetic nanoparticles (MNPs). The magnetic nanoparticles were modified by tetraethyl orthosilicate (TEOS) and 3-methacryloxypropyl trimethoxysilane (MPTS) before imprinting. The magnetic molecularly imprinted polymer (MMIP) was polymerized at the surface of modified MNPs by using of methacrylic acid (MAA) as functional monomer, 4-NP as template and ethylene glycol dimethacrylate (EGDMA) as cross-linker. Experimental design by the Taguchi method was used for the optimization of synthesis procedure of imprinted polymer. The resulting MMIP showed high adsorption capacity, proper selectivity and fast kinetic binding for the template molecule. It was characterized by Fourier transform infrared (FT-IR) analysis, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) methods. The maximum adsorption capacity of MMIP was obtained as 57.8 mg g−1 and it took about 2 h to achieve the equilibrium state. The adsorption curve of MMIP was also fitted with the Freundlich isotherm equation. The assay exhibited a linear range of 25–1000 μg L−1 for 4-NP with the correlation coefficient (R2) of 0.995. The method was also examined for the analysis of 4-NPs in seawater. For recovery evaluation, the seawater samples were spiked at two concentration levels of 50 and 100 μg L−1 of 4-NPs and the recovery values were in the range of 79.3–99.8%. The relative standard deviations (RSD) for the recoveries were less than 5.2%.