840 Acta Chim. Slov. 2007, 54, 840–848 Norouzi et al.: Non-electroactive Recognition: Pico-level Monitoring of Flunixin by Its Sub-second Adsorption ... Scientific paper Non-electroactive Recognition: Pico-level Monitoring of Flunixin by Its Sub-second Adsorption at Au Microelectrode by Fast Fourier Transforms Continuous Cyclic Voltammetric Technique (FFTCCV) Parviz Norouzi a, *, Mohammad Reza Ganjali a , Rassoul Dinarvand b , Sharareh Labbafi a a Center of Excellence in Electrochemistry, Department of Chemistry, University of Tehran, Tehran, Iran b Medical Nanotechnologycal Reserch center, University of Tehran/Medical Sciences, Tehran, Iran * Corresponding author: E-mail: Norouzi@khayam.ut.ac.ir Received: 25-05-2007 Abstract In this work a novel method for the determination of flunixin in flow-injection systems has been developed. The fast Fourier transform continuous cyclic voltammetry (FFTCV) at gold microelectrode in flowing solution system was used for determination of flunixin in its pharmaceutical formulations. The developed technique is very simple, precise, accu- rate, time saving and economical, compared to all of the previously reported methods. The effects of various parameters on the sensitivity of the method were investigated. The best performance was obtained with the pH value of 2, scan rate value of 30V s –1 , accumulation potential of –100 mV and accumulation time of 0.4 s. The proposed method has some advantages over other reported methods such as, no need for the removal of oxygen from the test solution, a picomolar detection limit, and finally the method is fast enough for the determination of any such compound, in a wide variety of chromatographic methods. The method was linear over the concentration range of 14–266400 pg/ml (r = 0.9975) with a limit of detection and quantitation 4 and 14 pg/ml, respectively. We used this method to determination of flunixin in tablets. Keywords: Flunixin, ultr-amicroelectrode, fast fourier transform cyclic voltammetry, flow injection. 1. Introduction Flunixin, Figure 6, was used for the treatment of ul- monarydiseases and endotoxin-induced mastitis, and an MRL value of 40 µg kg –1 in milk for its metabolite5- hydroxyflunixin was set in Council Regulation2377/90. Non-steroid anti-inflammatory agents (NSAID) are used in the treatment of bovine coliform mastitis in order to reduce the severity of the clinical signs, to improve cu- re and to minimise adverse effects of the disease. 1,2 The NSAID registered for veterinary use in Belgium are pyra- zolone derivatives (e.g. phenylbutazone), nicotinic acid derivatives (e.g. flunixine meglumine), fenamates (e.g. tolfenamic acid), arylpropionic acid derivatives (e.g. car- profen, ketoprofen) and the oxicam group (e.g. meloxi- cam). 3 As we were interested in residues of NSAID in milk, we selected two compounds, flunixin meglumine and ketoprofen, for this study, because these compounds are licensed for milk cows and a withdrawal time of 12 h after the last treatment was indicated in the instructions. Flunixin is used for the treatment of pulmonary diseases and endotoxin-induced mastitis, and an MRL value of 40 µg kg –1 in milk for its metabolite hydroxyflunixin was set in Council Regulation 2377/90. A number of analytical methods have been develo- ped for plasma and other biological fluids dogs and hor- ses. 4–10 A few methods have been applied to study the pharmacokinetics of flunixin in lactating cattle after sin- gle and multiple intramuscular and intravenous admini- stration, 11,12 and to detect flunixin in milk 13 and in muscle tissue. 14