Sensors and Actuators B 177 (2013) 887–892 Contents lists available at SciVerse ScienceDirect Sensors and Actuators B: Chemical journa l h o mepage: www.elsevier.com/locate/snb Nitrite determination at electrochemically synthesized polydiphenylamine-Pt composite modified glassy carbon electrode Binesh Unnikrishnan, Pu-Liang Ru, Shen-Ming Chen ∗ , Veerappan Mani Electroanalysis and Bioelectrochemistry Lab, Department of Chemical Engineering and Biotechnology, National Taipei University of Technology, No. 1, Section 3, Chung-Hsiao East Road, Taipei 106, Taiwan, ROC a r t i c l e i n f o Article history: Received 16 August 2012 Received in revised form 26 November 2012 Accepted 27 November 2012 Available online 6 December 2012 Keywords: Polydiphenylamine Platinum Nanoparticle Nitrite oxidation Amperometry a b s t r a c t Platinum nanoparticles found very wide application in electrocatalysis and sensor. However, Pt must be deposited in a stable matrix to increase stability and avoid fouling. In this work polydiphenylamine-Pt (PDPA-Pt) composite has been synthesized by electrochemical method on glassy carbon electrode. PDPA- Pt has been characterized by scanning electrochemical microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The SEM studies showed well dispersed Pt nanoparticles on PDPA surface. The electro- catalytic activity of PDPA-Pt film modified electrode toward the oxidation of NO 2 − was studied by cyclic voltammetry and amperometry. Cyclic voltammograms showed that NO 2 − undergoes irreversible oxida- tion at 0.85 V at PDPA-Pt modified electrode which is 0.33 V less than that of bare GCE. This shows the efficient electrocatalytic activity of the composite film. The electroanalytical application of the compos- ite film was done by amperometric technique. The film shows a response time of less than 1 s and wide linear range of detection from 1 M to 9.5 mM. PDPA-Pt is a promising material for electrochemical and biosensor applications. The good recoveries achieved in the various water samples for the determination of nitrite shows the practicality of the proposed sensor. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Nitrite is widely used as an antimicrobial agent [1] in cured and processed meats because it is a color and flavor enhancer. It is also present in vegetables and is a potential hazard to human health [2]. Nitrite is also found in water formed by natural process of nitro- gen cycle and also from the use of nitrate fertilizers. A portion of the nitrate in the fertilizers, human waste and animal waste are converted to nitrite by itself [3]. Nitrite is also used in different kinds of soups and the quantity of the nitrite in many soups are more than the allowed level set by the Joint Expert Committee on Food Additives (JECFA) [4]. A study by Cockburn et al. showed that the nitrite present in animal feed is not only toxic to the livestock that feed on it, but also to the humans who consume the meat [5]. Excess exposure of the livestock to nitrite cause accelerated pulse, dyspnea, muscle tremors, weakness, vomiting, unstable gait, and cyanosis leading to death. After ingestion, nitrite reacts with hemoglobin to form methaemoglobin in blood. Methaemoglobin cannot bind to oxygen and therefore causes a situation called methaeglobinamia [6,7]. Ferrucci et al. conducted a detailed study ∗ Corresponding author. Tel.: +886 2270 17147; fax: +886 2270 25238. E-mail address: smchen78@ms15.hinet.net (S.-M. Chen). on the potential carcinogenic effect of dietary nitrate and nitrite and the results shows the increased risk of bladder cancer [8]. Therefore the determination of nitrite in various food products, vegetables, drinking water, animal feeds, water resources, etc. are very important and essential to maintain the health of both humans and livestock. Several conventional methods like spectrometry [9], chro- matography [10,11], spectrophotometry [12] are reported for the determination of nitrite. However, a great deal of attention has been given for electrochemical methods due to their advantages over the conventional methods. Nitrite determination by elec- trooxidation of NO 2 − ion at modified electrodes has been reported [13–16]. Nitrite determination by electrooxidation of nitrite can avoid the interference of O 2 reduction reaction and other common interferrants [17]. Electrodes modified with metal nano particles [18,19], conducting polymers [20], metal oxides [21] have been used for the electrooxidation and determination of nitrite. In this study, a novel composite containing poly(diphenyl amine) (PDPA) and Pt nanoparticles has been synthesized by electrochemical method and characterized by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The electrocat- alytic activity of the PDPA-Pt composite has been studied by cyclic voltammetry (CV) in pH 4. The electroanalytical performance of the proposed film has been studied by amperometry. 0925-4005/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.snb.2012.11.102