Fe3O4 magnetic nanoparticles, with a negative charge surface, are known to have efficient adsorbent properties, but they tend to be agglomerated into larger aggregates or flocs, which can cause loss of specific area. The addition of cotton fibre, as a stabiliser in preparation of the Fe3O4 nanoparticles, is able to efficiently reduce particle aggregation, and thus, effective particle size, resulting in much greater specific surface area and adsorption sites. Fe3O4 nanoparticles synthesis was accomplished by in situ high-temperature decomposition of the precursor ferric ion in the presence of cotton fibre and ethylene glycol solvent. The morphology of Fe3O4 nanoparticles was characterised by field emission scanning electron microscopy and X-ray diffraction, which confirmed that the magnetic nanoparticles are highly dispersed. These Fe3O4 nanoparticles were used for clean-up and pre-concentration of Sudan dyes in chilli and hot red sauces, prior to their determination by capillary liquid chromatography diode array detection. A comparative study of analyte pre-concentration was conducted with magnetic nanoparticles prepared with and without cotton fibre showing that both solid phases adsorb the analytes, but higher recoveries were obtained when using cotton fibre which therefore was selected for extraction of Sudan dyes.
Keywords: Capillary liquid chromatography; cotton fibre; food samples; magnetic solid phase extraction Sudan dyes.