title: Determination of diclofenac on a dysprosium nanowire- modified carbon paste electrode accomplished in a flow injection system by advanced filtering.
abstract: A new detection technique called Fast Fourier Transform Square-Wave Voltammetry (FFT SWV) is based on measurements of electrode admittance as a function of potential. The response of the detector (microelectrode), which is generated by a redox processes, is fast, which makes the method suitable for most applications involving flowing electrolytes. The carbon paste electrode was modified by nanostructures to improve sensitivity. Synthesized dysprosium nanowires provide a more effective nanotube-like surface [1-4] so they are good candidates for use as a modifier for electrochemical reactions. The redox properties of diclofenac were used for its determination in human serum and urine samples. The support electrolyte that provided a more defined and intense peak current for diclofenac determination was a 0.05 mol L(-1) acetate buffer pH = 4.0. The drug presented an irreversible oxidation peak at 850 mV vs. Ag/AgCl on a modified nanowire carbon paste electrode which produced high current and reduced the oxidation potential by about 100 mV. Furthermore, the signal-to-noise ratio was significantly increased by application of a discrete Fast Fourier Transform (FFT) method, background subtraction and two-dimensional integration of the electrode response over a selected potential range and time window. To obtain the much sensivity the effective parameters such as frequency, amplitude and pH was optimized. As a result, C(DL) of 2.0 × 10(-9) M and an LOQ of 5.0 × 10(-9) M were found for the determination for diclofenac. A good recovery was obtained for assay spiked urine samples and a good quantification of diclofenac was achieved in a commercial formulation.
authors.affiliation: Center of Excellence in Electrochemistry, Department of Chemistry, University of Tehran, Tehran, Iran; E-Mails:  daneshgar@khayam.ut.ac.ir  (P.D.);  ganjali@khayam.ut.ac.ir  (M.R.G.).
authors.forename: Parandis
authors.initials: P
authors.lastname: Daneshgar
authors.forename: Parviz
authors.initials: P
authors.lastname: Norouzi
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Ganjali
authors.forename: Rasoul
authors.initials: R
authors.lastname: Dinarvand
authors.forename: Ali Akbar
authors.initials: AA
authors.lastname: Moosavi-Movahedi