ARTICLE IN PRESS JID: JTICE [m5G;June 13, 2016;9:24] Journal of the Taiwan Institute of Chemical Engineers 000 (2016) 1–9 Contents lists available at ScienceDirect Journal of the Taiwan Institute of Chemical Engineers journal homepage: www.elsevier.com/locate/jtice Electrochemical determination of aspirin and caffeine at MWCNTs-poly-4-vinylpyridine composite modified electrode Hanieh Ghadimi a,b,c,* , Ramin M.A.Tehrani d , Wan Jefrey Basirun b,e , Nurul Junaida Ab Aziz c , Norita Mohamed c , Sulaiman Ab Ghani c,** a Department of Chemical and Biomolecular Engineering, The University of Akron, Akron, OH 44325-3906, USA b Department of Chemistry, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia c Pusat Pengajian Sains Kimia, Universiti Sains Malaysia, 11800 Pulau Pinang, Malaysia d Department of Chemistry, Yadegar-e- Imam Khomeini (RAH) Shahre Rey Branch, Islamic Azad University, Tehran, Iran e Institute of Nanotechnology and Catalysis (NanoCat), University of Malaya, Kuala Lumpur 50603, Malaysia a r t i c l e i n f o Article history: Received 16 July 2015 Revised 19 May 2016 Accepted 25 May 2016 Available online xxx Keywords: Composite materials Modified electrodes MWCNT Poly (4-vinylpyridine) a b s t r a c t A highly sensitive voltammetric sensor for aspirin (ASA) and caffeine (CF) was fabricated on a glassy carbon electrode (GCE) modified with a composite film of poly (4–vinylpyridine) (P4VP) and multiwall carbon nanotubes (MWCNT). Cyclic voltammetry of P4VP–MWCNT/GCE indicated that the electrode re- action was a typical diffusion limiting process and the catalytic reaction of ASA and CF was observed in 0.1 M phosphate buffer (pH 7.4). For the detection of ASA, a 30 fold improvement was observed in the anodic peak current I pa , at P4VP–MWCNT/GCE compared to the bare GCE. At the optimum parameter, I pa was found to be linearly dependent on the concentrations of ASA (0.04–350 μM) and CF (2.0–200 μM). The detection limits were 4.42 nM and 1.19 nM for ASA and CF respectively. The differential pulse voltam- metry determination of ASA and CF in the presence of paracetamol (PCT) showed that ASA could be assayed in biological samples free from the interference of CF and PCT. The fabricated P4VP–MWCNT/GCE also displayed good stability, reproducibility and recovery in pharmaceutical and biological samples. Published by Elsevier B.V. on behalf of Taiwan Institute of Chemical Engineers. 1. Introduction Aspirin or acetylsalicylic acid (ASA) is a popular pharmaceuti- cal drug commonly used in the treatment of fever, headache and renal [1] and to some extent for Alzheimers [2,3], cancer [4] and cardiovascular illness [5, 6]. ASA and another pharmaceutical prod- uct, caffeine (CF) are usually found together in most formulation tablets. CF is used as a stimulant to reduce physical exhaustion and to restore alertness due to drowsiness [7,8]. These pharmaceutical products are known to have several physiological effects such as gastric acid secretion and dieresis [9]. The analysis of these two compounds is, therefore, an important necessity. Various analytical methods have been used for the determina- tion of ASA and CF such as spectrophotometry [10], spectroflu- * Corresponding author at: Department of Chemical and Biomolecular Engineer- ing, The University of Akron, Akron, OH 44325-3906, USA. Tel.: +12342819164; fax: +60379675330. ** Corresponding author. E-mail addresses: Hanieh.Ghadimi@yahoo.com, Hanieh.usm@gmail.com (H. Ghadimi), ramintehrani@hotmail.com (R. M.A.Tehrani), jeff@um.edu.my (W.J. Basirun), gurglez91_wajad@yahoo.com (N.J. Ab Aziz), noritamohamed@yahoo.com (N. Mohamed), sag@usm.my (S. Ab Ghani). orimetry [11], chromatography [12] and Raman spectroscopy [4]. But these methods suffer many drawbacks such as high cost, time consuming and complicated procedures. Electrochemical methods are not commonly used for the analysis of ASA and CF, due to their high oxidation potentials. However, electrochemical methods have received much attention lately, mainly due to their sensitiv- ity and simplicity. Electrodes such as multiwall carbon nanotube- alumina-coated silica nanocomposite modified glassy carbon elec- trodes [13], platinum electrode [14], nickel hydroxide-modified nickel electrode [15], and cobalt hydroxide nanoparticles mod- ified glassy carbon electrode [16], boron-doped diamond elec- trode [17] and in situ surfactant-modified MWCNT paste electrode [18] have all been employed for the determination of ASA and CF. Carbon nanotubes (CNTs) have received tremendous attention in electroanalysis due to their exceptional electrical conductiv- ity, chemical stability and mechanical strength [19,20]. However, its poor solubility and process-ability are the main obstacles for biomedical and other applications. The dispersion of CNT in con- ducting polymer matrix is an attractive option to produce the so- called solution mixing and has been used in the preparation of chemically modified electrode [21,22]. This is of special interest because they have three-dimensional structures due to the incor- poration of CNT in conducting polymers. The non-covalent and http://dx.doi.org/10.1016/j.jtice.2016.05.043 1876-1070/Published by Elsevier B.V. on behalf of Taiwan Institute of Chemical Engineers. Please cite this article as: H. Ghadimi et al., Electrochemical determination of aspirin and caffeine at MWCNTs-poly-4-vinylpyridine composite modified electrode, Journal of the Taiwan Institute of Chemical Engineers (2016), http://dx.doi.org/10.1016/j.jtice.2016.05.043