Hybrid nanoparticles based on magnetic multiwalled carbon nanotube-nanoC18SiO2 composites for solid phase extraction of mycotoxins prior to their determination by LC-MS

Abstract

The preparation of magnetic nanoparticles (MNPs) coated with a layer of octadecyl group-modified silica containing multiwalled carbon nanotubes (MWCNTs) is described. Synthesis was accomplished by in-situ high temperature decomposition of the precursors ferric ion, octadecyltrichlorosilane (C18) and MWCNTs in ethylene glycol solvent. Transmission electron microscopy confirmed that the MNPs are encapsulated in the composite silica coating. These MNPs were used for clean-up of maize samples and the preconcentration of zearalenone and its secondary metabolites, namely β-zearalenol, β-zearalanol, α-zearalenol, α-zearalanol, and zearalanone at trace levels, prior to their determination by liquid chromatography-mass spectrometry. A comparative study of analyte adsorption and desorption was conducted with MNPs prepared with and without C18 and showed both solid phases to adsorb the analytes to some extent, but higher recoveries were obtained by using the C18-modified MNPs which therefore was selected for extraction of the mycotoxins. Under the optimum conditions, the MNPs can be re-used 6 times at least without loss of their extraction efficiency. Preconcentration factors are ~25, detection limits range from 0.6 to 1.0 μg mL−1, recoveries from spiked samples from 91.6 to 98.3 %, and relative standard deviations are <3.9 %.