ORIGINAL PAPER An electrochemical sensor based on carbon nanotubes and a new Schiff base for selective determination of dopamine in the presence of uric acid, folic acid, and acetaminophen Mohammad Mazloum-Ardakani & Abolfazl Naser-Sadrabadi & Mohammad Ali Sheikh-Mohseni & Ali Benvidi & Hossein Naeimi & Azam Karshenas Received: 1 January 2013 / Revised: 12 February 2013 / Accepted: 19 February 2013 # Springer-Verlag Berlin Heidelberg 2013 Abstract In this paper, the electrochemical properties of a carbon paste electrode modified by a synthesized Schiff base, 2,2′-[1,4-phenylenediyl-bis(nitrilomethyl-idene)]-bis (4-hydroxyphenol), and carbon nanotubes were studied by cyclic voltammetry. The modified electrode was used as an electrochemical sensor for catalytic oxidation of dopamine (DA). Differential pulse voltammetry (DPV) of DA by this electrochemical sensor exhibited two linear dynamic ranges with a detection limit (3σ) of 0.42 μM. Also, the selectivity of the prepared electro- chemical sensor was checked for determination of DA in the presence of uric acid (UA), folic acid (FA), and acetaminophen (AC). The DPV results indicate that the proposed sensor can be used for simultaneous determina- tion of DA, UA, and FA and also simultaneous determina- tion of DA and AC. Finally, the proposed electrochemical sensor was used for determinations of these substances in real sample. Keywords Selective determination . Carbon nanotubes . Dopamine . Uric acid . Folic acid . Acetaminophen Introduction Dopamine (DA) is one of the most significant catechol- amines and plays an important role in neurotransmission [1–4]. It is well known that upon abnormal dopamine trans- mission, several neurological disorders, e.g., Schizophrenia, Huntington’ s disease, and Parkinson’ s disease would occur [5, 6]. Therefore, determination of the concentrations of DA is useful. DA can be determined by different analytical methods [7]. Also, as DA can be oxidized electrochemically, its determination has been widely studied by electroanalytical techniques [8, 9]. Uric acid (UA) is a primary end product of purine me- tabolism. Abnormal levels of UA are symptoms of several diseases, such as gout, hyperpiesia, and Lesch–Nyhan syn- drome [10]. Hence, monitoring of the concentration of UA in biological fluids may be used as an early warning of the presence of these diseases [11]. Colorimetric, enzymatic, and electrochemical methods are used to determine the concentration of UA [12]. Electrochemical sensors for the determination of UA are more selective, less expensive, and less time consuming than the other methods [13]. Folic acid (FA) is necessary for cell development, for metabolism of specific biochemical reactions in the body, and for the metabolism of specific anticonvulsant drugs. FA has an interrelationship with vitamin B12 [14]. FA can be determined by various instrumental methods and electro- chemical sensors [15, 16]. Acetaminophen (AC) is a drug as pain relievers and fever reducers. When used correctly, side effects are rare, but seri- ous side effect such as liver damage due to large doses, chronic use, or concomitant use with alcohol or other drugs can occur. Some instrumental methods such as HPLC [17] and spectrophotometry [18] have been used for determination of M. Mazloum-Ardakani (*) : A. Naser-Sadrabadi : A. Benvidi Department of Chemistry, Faculty of Science, Yazd University, Yazd 89195-741, Iran e-mail: mazloum@yazduni.ac.ir M. A. Sheikh-Mohseni Faculty of Education Center of Miandoab, Urmia University, Urmia, Iran H. Naeimi : A. Karshenas Department of Organic Chemistry, Faculty of Chemistry, University of Kashan, Kashan 87317, Iran Ionics DOI 10.1007/s11581-013-0879-0 Downloaded from http://paperhub.ir