Fabrication and Characterization of LaF₃/Titania Nanotube Array Electrode for Determination of Fluoride Using a Headspace Single-Drop Microextraction System

Abstract

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 × 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%.

Keywords:

• Anodic oxidation
• Fluoride ion response
• Headspace SDME
• TiO₂ nanotube arrays

Acknowledgments

Financial support from the National Natural Science Foundation of China (21175047) and the National Science and Technology Special Foundation of China (2009ZX07529-002) are gratefully acknowledged.

Notes

^a Fluoride in toothpaste (wt %) is 0.15%.

^b Fluoride in toothpaste (wt %) is 0.11%.

^c Fluoride in toothpaste (wt %) is 0.04%.