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

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 (C-18) 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 beta-zearalenol, beta-zearalanol, alpha-zearalenol, alpha-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 C-18 and showed both solid phases to adsorb the analytes to some extent, but higher recoveries were obtained by using the C-18-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 similar to 25, detection limits range from 0.6 to 1.0 mu g mL(-1), recoveries from spiked samples from 91.6 to 98.3 %, and relative standard deviations are < 3.9 %.