Voltammetric determination of norepinephrine in the presence of acetaminophen using a novel ionic liquid/multiwall carbon nanotubes paste electrode Sadegh Salmanpour a , Toktam Tavana b , Ali Pahlavan c , Mohammad A. Khalilzadeh d, ⁎, Ali A. Ensafi e , Hassan Karimi-Maleh d, ⁎, Hadi Beitollahi f , Elaheh Kowsari g , Daryoush Zareyee b a Department of Chemistry, Sari Branch, Islamic Azad University, Sari, Iran b Department of Chemistry, Qaemshahr Branch, Islamic Azad University, Qaemshahr, Iran c Department of Physics, Science and Research Branch, Islamic Azad University, Mazandaran, Iran d Department of Chemistry, Science and Research Branch, Islamic Azad University, Mazandaran, Iran e Department of Chemistry, Isfahan University of Technology, Isfahan, Iran f Environment Department, Research Institute of Environmental Sciences, International Center for Science, High Technology & Environmental Sciences, Kerman, Iran g Department of Chemistry, Amirkabir University of Technology, No. 424, Hafez Avenue, Tehran, Iran abstract article info Article history: Received 20 September 2011 Received in revised form 19 January 2012 Accepted 22 May 2012 Available online 28 May 2012 Keywords: Norepinephrine Acetaminophen Ionic liquid Multiwall carbon nanotubes Voltammetry A novel multiwall carbon nanotubes (MWCNTs) modified carbon ionic liquid electrode (CILE) was fabricated and used to investigate the electrochemical behavior of norepinephrine (NP). MWCNTs/CILE was prepared by mixing hydrophilic ionic liquid, 1-methyl-3-butylimidazolium bromide (MBIDZBr), with graphite powder, MWCNTs, and liquid paraffin. The fabricated MWCNTs/CILE showed great electrocatalytic ability to the oxi- dation of NE. The electron transfer coefficient, diffusion coefficient, and charge transfer resistant (R ct ) of NE at the modified electrode were calculated. Differential pulse voltammetry of NE at the modified electrode exhibited two linear dynamic ranges with slopes of 0.0841 and 0.0231 μA/μM in the concentration ranges of 0.3 to 30.0 μM and 30.0 to 450.0 μM, respectively. The detection limit (3σ) of 0.09 μM NP was achieved. This modified electrode exhibited a good ability for well separated oxidation peaks of NE and acetaminophen (AC) in a buffer solution, pH 7.0. The proposed sensor was successfully applied for the determination of NE in human urine, pharmaceutical, and serum samples. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Norepinephrine (NE) is one of the derivatives of catecholamines secreted in the adrenal medulla and plays an important physiological role in the central nervous system. It affects muscle and tissue control, stimulates arteriole contraction, decreases peripheral circulation and activates lipolysis in adipose tissue [1]. It is also critical in mental dis- ease, heart failure; DNA breaks in cardiac myoblast cells, and diabetes. Recent reports have indicated that NE enhances adhesion of human immunodeficiency virus-1 (HIV-1)-infected leukocytes to cardiac micro-vascular endothelial cells and also accelerates HIV replication via proteinkinase [2]. On the other hand, NE is a drug belonging to the stimulants that are on the World Anti-Doping Agency's 2005 Prohibited List. So it is very necessary to develop fast, accurate and sensitive methods for its direct determination. Various methods, in- cluding spectrophotometry [3], capillary electrophoresis [4], and high-performance liquid chromatography [5] have been employed to the determination of NE. Because NE is an electroactive compound, its electrochemical detection has been the focus of research for elec- troanalytical researchers and neurochemists and some modified elec- trodes have been used to determine NE [6,7]. However, the irreversibility of its electrochemical property results in a large over- potential and the shape of the wave is not good at the conventional electrode. In order to resolve these problems, some modified elec- trodes have been used to determine NE [8,9], and different forms of carbon are the most interesting electrode materials. This is mainly be- cause of their electrochemical stability and relatively high resistance against electrode fouling in physiological environments. Acetaminophen (AC) is a widely used anti-pyretic and analgesic drug with actions similar to aspirin. It is an effective and safe agent for the relief of mild to moderate pain associated with headache, arthritis and postoperative pain. Its ready access has resulted in its increased use in attempted suicide [10]. Many methods have been so far reported for its determination that include titrimetry [11,12], spectrophotometry [13–16], high performance liquid chromatography [17–20], capillary electrophoresis [21,22], fluorimetry [23], and electrochemical methods [24–30]. AC administration is known to increase brain serotonin (5-HT) levels as a result of liver tryptophan-2,3-dioxygenase (TDO) inhibition [31] and 5-HT is known to play a role in NE release in the brain [32,33]. Therefore, simultaneous determination of NE and AC is very important. Materials Science and Engineering C 32 (2012) 1912–1918 ⁎ Corresponding authors. Tel.: + 98 911 2540112(mobile); fax: + 98 311 391 2350. E-mail addresses: khalilzadeh73@yahoo.com (M.A. Khalilzadeh), h.karimi.maleh@gmail.com (H. Karimi-Maleh). 0928-4931/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.msec.2012.05.038 Contents lists available at SciVerse ScienceDirect Materials Science and Engineering C journal homepage: www.elsevier.com/locate/msec