Determination of Rhodamine B in Cosmetics, Candy, Water, and Plastic by a Novel Multiwalled Carbon Nanotube (MWCNT)@Zinc Oxide@Magnetite Nanocomposite for Magnetic Solid-Phase Extraction (MSPE) with Spectrophotometric Detection.

A new magnetic solid phase microextraction method (MSPE) was developed for the preconcentration of rhodamine B from plastics, cosmetics, and environmental samples before spectrophotometric analysis. A nanocomposite adsorbent containing ZnO nanoparticles (NPs), multi-walled carbon nanotubes (MWCNTs) and Fe₃O₄ nanoparticles was synthesized by a hydrothermal procedure. The new magnetic nanocomposite (MWCNTs@ZnO@Fe₃O₄) was characterized by Fourier-transform infrared spectroscopy (FT-IR), x-ray diffraction (XRD), and scanning electron microscopy (SEM). The pH, sample volume, eluent type, adsorbent mass, influence of foreign species, and analyte-adsorbent and eluent contact times were optimized. The optimum pH was 3; adsorbent mass, 20 mg; sample volume, 50 mL; and eluent, 0.7 mL of ethanol. Recovery values exceeding 95% were obtained. The developed vortex assisted magnetic solid phase extraction method (VA-MSPE) was applied to practical analysis. The limits of detection (LOD) and quantification (LOQ) were 0.83 µg L⁻¹ and 2.77 µg L⁻¹, respectively. The addition/recovery experiments were carried on several water samples to demonstrate acceptable recoveries. [ABSTRACT FROM AUTHOR]