Magnetic solid-phase extraction and pre-concentration of 17β-estradiol and 17α-ethinylestradiol in tap water using maghemite-graphene oxide nanoparticles and determination via HPLC with a fluorescence detector

Abstract

This work presents the synthesis and application of magnetic nanoparticles of graphene oxide (GO)/γ-Fe2O3 as a sorbent for solid-phase extraction and pre-concentration of estrogens in tap water samples followed by the determination using high-performance liquid chromatography with fluorescence detector. The GO/γ-Fe2O3 nanoparticles were synthesized via co-precipitation and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, N2 adsorption-desorption and scanning electron microscopy. The adsorption of estrogens was performed after the optimization of the domain for the factors time, pH, and nanoparticle/analyte ratio using a central composite design consisting of eight factorial points (23), six axial points, and five replicates of the central point. The optimal adsorption conditions were obtained at 40 min, pH 6, and 9 mg of magnetic nanoparticles (nanoparticle/analyte concentration ratio = 45000). The analytes were eluted using 500 µL of a solution composed of ethanol/water/acetic acid (80:20:1, v/v/v). The enrichment factor achieved were 91 ± 6 for 17β-estradiol and 119 ± 7 for 17α-ethinylestradiol, whereas the limits of detection achieved for 17β-estradiol and 17α-ethinylestradiol were 2.7 and 0.8 ng L−1, respectively. Recovery tests ranged from 83 to 98%, and the short-term precision was % RSD ≤ 7 (n = 10).