FABRICATION AND CHARACTERIZATION OF LAF3/TITANIA NANOTUBE ARRAY ELECTRODE FOR DETERMINATION OF FLUORIDE USING A HEADSPACE SINGLE-DROP MICROEXTRACTION SYSTEM

LaF3/titania nanotube array (TNAs) electrodes were fabricated by electrodeposition of LaF3 on synthesized TNAs. The electrode was characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), and energy dispersive X-ray spectrometer (EDS). The electrode exhibited excellent response to fluoride ion. The linear calibration range achieved four orders of magnitude of F- concentration (10(-6)-10(-2) mg/ml) and the sensitivity of the electrode is higher than that of ordinary fluoride ion selective electrodes (mode PF-1). The limit of detection (LOD) was estimated to be 4.39 x 10(-7) mg/ml (S/N = 3). The novel electrode was applied to the determination of trace fluoride ions in tap water and toothpaste. Finally, a headspace single-drop microextraction (SDME) system coupled with LaF3/TNAs electrode was successfully applied to determine fluoride in milk samples. The results are satisfactory with an average relative standard deviation (RSD %) of 0.51% and recovery from 96.3% to 107.3%.