DOI: 10.1002/elan.201600221 Selective and Sensitive Nitrite Sensor Based on Glassy Carbon Electrode Modified by Silver Nanochains Tayyaba Shaikh, [a] Zaffar Hussain Ibupoto,* [b, f] Farah N. Talpur, [a] Sirajuddin, [a] Abdul Rauf Khaskheli, [c] Muhammad H. Agheem, [d] Samia Siddiqui, [a] Aneela Tahira, [b] Magnus Willander, [e] and Cong Yu [f] 1 Introduction Nitrite is recognized as an essential source of nitrogen in green plants and it is completely reduced in nature by the enzyme nitrite reductase [1]. It is widely employed as fer- tilizing agent [2], corrosion inhibitor and food preserva- tive [3]. Monitoring of nitrite levels in food stuffs and water systems began receiving increasing concerns due to its environmental and health implications [4]. The World Health Organization (WHO) has established a permissible limit of 3 mg L 1 for nitrite in drinking water [5]. The presence of excessive nitrite in blood induces the oxida- tion of hemoglobin leading to life threatening condition called as methaemoglobinaemia or blue baby syndrome [6]. Presence of nitrite in food and drinking water is also a subject of significant concern due to its association with the development of stomach cancers [7]. Therefore there Abstract : Herein, we report a facile method for the syn- thesis of silver nanochains (Ag nanochains) using pyri- dine as growth directing agent and citrate ions as capping agents in alkaline medium. The characterization of the synthesized high aspect ratio Ag nanochains was accom- plished with the help of Transmission Electron Microsco- py (TEM) and High Resolution Transmission Electron Microscopy (HRTEM) which demonstrates the thickness below 100 nm. Crystalline nature of the synthesized Ag nanochains was investigated using X-ray diffractrometry. A sensitive electrochemical nitrite sensor was assembled using synthesized Ag nanochains as electrode modifier. An improved cyclic voltammetric response for the oxida- tion of nitrite ions was witnessed at the modified GCE surface in comparison to bare GCE in Britton Robinson (BR) buffer (pH 4). The influence of pH on the oxidation peak current of nitrite ions was also examined using cyclic voltammetry. The electrocatalytic oxidation cur- rents attained through amperometric measurements at Ag nanochains modified GCE were linearly dependent on the concentration of nitrite ions in the two ranges of 0.5–7.5 mM, 5–480 mM. Linear calibration plots of Ip vs. concentration of nitrite were also constructed at the pro- posed sensor using square wave voltammetry and differ- ential pulse voltammetry. The proposed sensing strategy was successfully employed for the determination of nitrite in water samples with excellent recoveries. Keywords: silver nanochains · cyclic voltammetry · amperometry · nitrite ions [a] T. Shaikh, F.N. Talpur, Sirajuddin, S. Siddiqui National Center of Excellence in Analytical Chemistry University of Sindh Jamshoro 76080 Pakistan [b] Z. H. Ibupoto, A. Tahira Dr. M. A. Kazi Institute of Chemistry University of Sindh Jamshoro 76080 Pakistan + 92 9213429 *e-mail: zaffar_ibupoto@yahoo.com [c] A. R. Khaskheli Department of Pharmacy Shaheed Mohtarma Benazir Bhutto Medical University Larkana [d] M. H. Agheem Center for Pure and Applied Geology University of Sindh Jamshoro 76080 Pakistan [e] M. Willander Department of Science and Technology, Campus Norrkoping Linkoping University SE-60174 Norrkoping Sweden [f] Z. H. Ibupoto, C. Yu State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun 130022 PR China Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/elan.201600221. www.electroanalysis.wiley-vch.de  2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Electroanalysis 2016, 28, 1 – 9 &1& These are not the final page numbers! ÞÞ Full Paper