title: Carbon coated titanium dioxide nanotubes: synthesis, characterization and potential application as sorbents in dispersive micro solid phase extraction.
abstract: In this article, carbon coated titanium dioxide nanotubes (c-TNTs) have been synthesized. The synthesis of the bare TNTs (b-TNTs) using anatase as precursor and their coating with a caramel layer have been performed by simple and cheap hydrothermal processes. The final conversion of the caramel layer in a carbon coating has been accomplished by a thermal treatment (600°C) in an inert (Ar) atmosphere. The c-TNTs have been characterized by different techniques including transmission microscopy, infrared spectroscopy, X-ray powder diffraction, thermogravimetry and Brunauer, Emmett and Teller (BET) adsorption isotherms. The extraction performance of the c-TNTs under a microextraction format has been evaluated and compared with that provided by b-TNTs and multiwalled carbon nanotubes (MWCNTs) using naproxen and ketoprofen as model analytes. c-TNTs provided better results than the other nanoparticles, especially at low acidic pH values. In addition, c-TNTs presented a better dispersibility than MWCNTs, which is very interesting for their use in dispersive micro-solid phase extraction. Finally, a microextraction format, adapted to low sample volumes, has been proposed and applied for the determination of naproxen and ketoprofen in saliva and urine samples by liquid chromatography with UV detection. The results indicate that this approach is promising for the analysis of biological samples. In fact, the recoveries were in the range between 96% and 119% while the precision, expressed as relative standard deviation, was better than 8.5% and 26.3% for urine and saliva, respectively. The detection limits were in the range 34.1-40.8μg/L for saliva samples and 81.1-110μg/L for urine samples.
authors.affiliation: Department of Analytical Chemistry, Institute of Fine Chemistry and Nanochemistry, Marie Curie Building, Campus of Rabanales, University of Córdoba, 14071 Córdoba, Spain.
authors.forename: M T
authors.initials: MT
authors.lastname: García-Valverde
authors.affiliation: Department of Analytical Chemistry, Institute of Fine Chemistry and Nanochemistry, Marie Curie Building, Campus of Rabanales, University of Córdoba, 14071 Córdoba, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Lucena
authors.affiliation: Department of Analytical Chemistry, Institute of Fine Chemistry and Nanochemistry, Marie Curie Building, Campus of Rabanales, University of Córdoba, 14071 Córdoba, Spain.
authors.forename: F
authors.initials: F
authors.lastname: Galán-Cano
authors.affiliation: Department of Analytical Chemistry, Institute of Fine Chemistry and Nanochemistry, Marie Curie Building, Campus of Rabanales, University of Córdoba, 14071 Córdoba, Spain.
authors.forename: S
authors.initials: S
authors.lastname: Cárdenas
authors.affiliation: Department of Analytical Chemistry, Institute of Fine Chemistry and Nanochemistry, Marie Curie Building, Campus of Rabanales, University of Córdoba, 14071 Córdoba, Spain. Electronic address: qa1meobj@uco.es.
authors.forename: M
authors.initials: M
authors.lastname: Valcárcel
mesh_terms: D000327:Adsorption; D002244:Carbon / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles / Q000737:chemistry; D037742:Nanotubes, Carbon / Q000737:chemistry* / Q000648:ultrastructure; D052616:Solid Phase Extraction / Q000379:methods*; D017550:Spectroscopy, Fourier Transform Infrared; D013818:Thermogravimetry; D014025:Titanium / Q000737:chemistry*
chemical_list: D037742:Nanotubes, Carbon; C009495:titanium dioxide; D002244:Carbon; D014025:Titanium
keywords: Carbon coated titanium dioxide nanotubes; Dispersive micro-solid phase extraction; Drugs; Multiwalled carbon nanotubes; Saliva; Urine