Antipassivating Electrochemical Process of Glassy Carbon Electrode (GCE) Dedicated to the Oxidation of Nitrophenol Compounds M. PontiØ,* a G. Thouand, b F. De Nardi, a I. Tapsoba, c S. Lherbette a a GEPEA UMR-CNRS 6144, a-LUNAM, Angers University, Group Analysis & Processes (GA&P), 2 Bd. Lavoisier, 49045 Angers cedex 01, France phone: (+ 33) 2 41 73 52 07, fax : (+ 33) 2 41 73 54 21 b GEPEAUMR-CNRS 6144, LUNAM, Nantes University, CBAC group, IUT La Roche/Yon, 18 Bd. Gaston Defferre, 85035 La Roche/Yon, France c University of Ouagadougou, UFR-SEA, Laboratory of Organic Chemistry, BP7021 Ouagadougou 03, Burkina Faso *e-mail: maxime.pontie@univ-angers.fr Received: February 14, 2011; & Accepted: April 4, 2011 Abstract We report for the first time a novel electrochemical treatment applied to a glassy carbon electrode (GCE) during p- nitrophenol (PNP) oxidation and dedicated to the limitation of electrode passivation by nitrophenol compounds ox- idation. We propose an electrochemical process of direct phenol oxidation by starting the electrolysis at a very low potential, 1.2 V/SCE, in order to generate a soluble monomer, p-aminophenol, on the electrode surface. Then, p- aminophenol elaborated on the electrode surface in the place of oligomers, gives benzoquinone as a by-product and no film formation was observed. Furthermore, the presence of a p-NiTSPc (film of nickel tetrasulfonated phtalocya- nine) coating permitted to increase two times the electrode sensitivity without passivation, too. Keywords: GCE, p-Nitrophenol (PNP), Electrooxidation, Electrochemical antipassivation, Nickel tetrasulfonated phtalocyanine film DOI: 10.1002/elan.201100082 1 Introduction Nitroaromatic compounds are recognized as environmen- tally hazardous and are widely used for the industrial pro- duction of dyes, pesticides, plasticizers, explosives and sol- vents. Nitrophenol compounds are significant environ- mental and food chain pollutants [1–8]. para-Nitrophenol (PNP), as methylparathion (MPT) main hydrolysis by- product, is responsible for methemoglobinemia [3]. Human exposure to MPT can be assessed by measuring the concentration of its metabolite PNP in urine [8]. Fur- thermore, PNP is a usable model chemical pollutant in the elaboration of biodegradability tests due to its erratic biodegradability [9]. Recently, water remediation by bio- logical systems has attracted worldwide attention to de- contaminate nitro-aromatics polluted sources. Oxidative and reductive mechanisms for biodegradation of nitro- phenol compounds have been reported [4]. A Moraxella sp. utilizes 4-nitrophenol as a sole source of carbon and nitrogen via an initial monooxygenase-catalyzed elimina- tion of nitrite, [4, 10] and also electrochemical degrada- tion conducted on carbon boron-doped diamond [11–13] and Bi-doped PbO 2 [14] electrodes. Moreover, ampero- metric detection of nitrophenol compounds was devel- oped by Wang et al. [2, 15, 16]. For rapid analyses under field conditions, high sensitive analytical tools (under ppb) with direct determination and in situ PNP determi- nation, it is urgent to elaborate rapid warning and field deployment, more compact low-cost instruments, coupled to smaller sensing probes and reusable, limiting passiva- tion of electrode materials. Usually the electrochemical determination of nitrophe- nol compounds occurred on direct nitro reduction. Fan et al. [17] proposed for PNP determination a ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate-single- walled carbon nanotube paste coated glassy carbon elec- trode with a limit of detection (LOD) of 250 mg/L. Re- cently, Moraes et al. [18] proposed a multiwall carbon nanotubes (MWCNT) sensor dedicated to PNP in natural waters with a LOD between 75 and 250 mg/L. Hutton et al. [19] using a Bismuth film electrode associated to the square wave voltammetry (SWV) method obtained a LOD of 1.4 mg/L. Recently, a sensitive type C/p-NiTSPc carbon fiber microelectrode (CFME) for PNP pollutant based on the direct reduction of nitro-function and a final LOD of 0.1 mg/L, was reported [20, 21]. Indirect nitroxylamine oxidation was also reported [18, 22, 23], but rarely PNP was determined by direct phenol oxidation due to blocking electrode surface with polymeric oxidation products leading to passivation of Electroanalysis 2011, 23, No. 7, 1579 – 1584  2011 Wiley-VCH Verlag GmbH &Co. KGaA, Weinheim 1579 Full Paper