Preparation, characterization and application of octadecyl modified magnesium oxide microspheres

A new solid-phase extraction sorbent, octadecyl modified magnesium oxide (C18-MgO) microspheres, was successfully prepared in the present work. Its composition, morphology and structure were studied by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), N(2) adsorption-desorption technique, and solid-state nuclear magnetic resonance (NMR). The as-synthesized C18-MgO was employed as a solid-phase extraction sorbent for the enrichment of polycyclic aromatic hydrocarbons (PAHs) in aqueous solutions. Several factors affecting the extraction efficiency of PAHs, including the type and concentration of organic modifiers, flow rate, sample volume, and the types of rinsing solvents and eluting solvents, were investigated systematically. The results demonstrated that C18-MgO was superior to MgO in terms of large volume in loading samples. In comparison with MgO and Sep-Pak C18, C18-MgO exhibited excellent extraction efficiency (>91% except for naphthalene) in respect of high recoveries under the optimized conditions. The limits of detection varied from 0.001 to 0.603 ng mL(-1) for 15 PAHs using high-performance liquid chromatography coupled with a fluorescence detector, indicating that the analytical method was highly sensitive. The proposed method was applied to enrich PAHs in tap water and acceptable recoveries (18-96%) were obtained.