Carbon ceramic electrodes modified with mixed oxides SiO2/SnO2 for determination of levofloxacin

The preparation of a carbon ceramic electrode modified with SnO2 (CCE/SnO2) using tin dibutyl diacetate as precursor was optimized by a 2(3) factorial design. The factors analyzed were catalyst (HCl), graphite/organic precursor ratio, and inorganic precursor (dibutyltin diacetate). The statistical treatment of the data showed that only the second-order interaction effect, catalyst x inorganic precursor, was significant at 95% confidence level, for the electrochemical response of the system. The obtained material was characterized by scanning electron microscopy (MEV), X-ray diffraction (XRD), RAMAN spectroscopy, XPS spectra, and voltammetric techniques. From the XPS spectra, it was confirmed the formation of the Si-O-Sn bond by the shift in the binding energy values referred to Sn 3d3/2 due to the interaction of Sn with SiOH species. The incorporation of SnO2 provided an increment of the electrode response for levofloxacin, with Ipa = 147.0 mu A for the ECC and Ipa = 228.8 mu A for ECC/SnO2, indicating that SnO2 when incorporated into the silica network enhances the electron transfer process. Under the optimized working conditions, the peak current increased linearly with the levofloxacin concentration in the range from 6.21x10(-5) to 6.97x10(-4) mol L-1 with quantification and detection limits of 3.80x10(-5) mol L-1 (14.07 mg L-1) and 1.13x10(-5) mol L-1 (4.18 mg L-1), respectively.