Magnetic coffee residue as sorbent for magnetic solid-phase extraction and determination of titanium dioxide nanoparticles in water samples.

Herein, we report a simple, efficient, and cost-effective solid-phase extraction method using magnetic coffee residue as adsorbent for extraction and determination of titanium dioxide nanoparticles (TiO₂ NPs) from environmental water samples. The adsorbent was prepared by modifying spent coffee residue using magnetite nanoparticles as magnetic medium through modified chemical precipitation technique, and the TiO₂ NPs were synthesized by a sol–gel method. The prepared materials were characterized by X-ray diffractometry, scanning electron microscopy, dynamic light scattering, and Fourier transform infrared spectroscopy. Factors affecting the extraction conditions were optimized, including effect of pH (4), sample volume (25 mL), amount of adsorbent (0.075 g), vortexing time (3 min), initial concentration (70 mg L^–1) and the desorption conditions. Under optimum conditions, the developed method exhibited high extraction efficiency (94%), a wide linear range (100–500 μg L^–1) and a limit of detection (LOD) of 12 µg L^–1. Moreover, the method showed excellent intra- and inter-day precision, with relative standard deviations (% RSD) of 3.47% and 4.58%, respectively. More importantly, the current method demonstrated great potential for the extraction and quantification of TiO₂ NPs in river, lake and effluent water samples and exhibited good percentage recovery. Therefore, the developed method can be used for monitoring level of TiO₂ NPs in different sample matrices. [ABSTRACT FROM AUTHOR]