Preparation of magnetic carbon nanotubes for separation of pyrethroids from tea samples

Magnetic carbon nanotubes (MCNTs) have been synthesized by chemical deposition of Fe3O4 nanoparticles onto carbon nanotubes. They were characterized by Fourier transform infrared spectroscopy, scanning electron microscope, X-ray diffraction and physical property measurement system. The MCNTs were used as the sorbents for the extraction of pyrethroids including beta-cyfluthrin, cyhalothrin and cyphenothrin from tea samples. The extraction conditions, such as the amount of magnetic sorbent, shaking time and rate, washing and eluting solution have been fully investigated. The analytes desorbed from MCNTs were determined by HPLC with UV detection. Under the optimal conditions, the linearity of the method is in the range of 0.05-25 mu g g(-1). The limits of detection of the three pyrethroids are 0.017, 0.010 and 0.018 mu g g(-1), respectively. The relative standard deviations of within- and between-day range from 3.5 % to 6.4 %, and from 4.5 % to 29 7.3 %, respectively. In all three spiked levels (0.05, 0.5 and 5 mu g g(-1)), the recoveries of pyrethroids are in the range of 82.2 %-94.4 %. This method is much faster and more effective than traditional methods, and it is promising for the analysis of pesticides residues.