Fabrication of multi-walled carbon nanotubes/oxide reinforced hollow fibers by sol-gel technique for rapid determination of metronidazole in milk

Three types of multi-walled carbon nanotubes (MWCNTs)/oxide reinforced hollow fibers, i.e. MWCNTs/SiO2, MWCNTs/TiO2, MWCNTs/ZrO2, based on sol-gel techniques were fabricated, compared and applied to extract metronidazole in milk samples by solid phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS). The factors influencing the extraction and desorption process were optimized, and the adsorption mechanism of MWCNTs/SiO2 reinforced hollow fibers was briefly discussed. MWCNTs/SiO2 reinforced hollow fiber might be selective to some organic compounds due to specific and non-specific adsorption of MWCNTs and SiO2 nanoparticles. It was found that the method provided linear range from 0.01-1000 mg L-1 (R = 0.9985), low detection limit of 0.01 mg L-1, preferable recoveries (69-96%) at three different concentrations. The obtained results demonstrated that MWCNTs/SiO2 hollow fiber solid phase microextraction could become a potential tool for quality control to monitor the amount of metronidazole residues in milk products.