Sensors and Actuators B 192 (2014) 648–657 Contents lists available at ScienceDirect Sensors and Actuators B: Chemical journal h om epage: www.elsevier.com/ locate/snb Voltammetric monitoring of Cd (II) by nano-TiO 2 modified carbon paste electrode sensitized using 1,2-bis-[o-aminophenyl thio] ethane as a new ion receptor Soleyman Ramezani a,∗ , Massoud Ghobadi b , Babak Nemati Bideh c a Faculty of Chemistry, Kharazmi (Tarbiat Moallem) University, Tehran, Iran b Department of Chemistry, Faculty of Science, Ilam University, Ilam, Iran c Faculty of Chemistry, Sharif University of Technology, Tehran, Iran a r t i c l e i n f o Article history: Received 27 August 2013 Received in revised form 6 November 2013 Accepted 12 November 2013 Available online 20 November 2013 Keywords: Carbon paste electrode TiO2NPs Differential pulse voltammetry (DPV) Cadmium (II) a b s t r a c t The objective of the work ahead is presentation of a new carbon paste electrode (CPE) modified by TiO 2 nanoparticles (TiO 2 NPs) and 1,2-bis-[o-aminophenyl thio] ethane (APTE) ligand as a selective cation receptor for determination of the Cd (II) ions using differential pulse anodic stripping voltammetry (DPASV). The electrode shows an excellent tendency to Cd (II) ions in presence of some interfering species. Under the optimum conditions, a linear calibration curve was obtained in the concentration range of 2.9 nM to 4.6 M with a correlation coefficient of 0.9969 in the anodic potential of 0.54 (V vs. Ag/AgCl). The metal detection limit was 2.0 nM after 10 min preconcentration (S/N = 3). The sensor shows high applicability in solutions with the optimal pH of 9.0 adjusted by 0.1 M phosphate buffer as supporting electrolyte and open circuit accumulation optimum time of 10 min. The stability of the modified elec- trode was studied in the period of 2 months week by week. The results showed that for a series of several determinations of Cd (II) at 25 M relative standard deviations (RSDs) are below 3.4% for modified CPEs. Eventually, the electrode was successfully used for determination of Cd (II) in tap water, Livergol herbal medicine and garden soil aqueous samples. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Undoubtedly, cadmium is one of the environmental countless hazards, and it’s exposures to environment comes primarily from fossil fuel combustion, phosphate fertilizers, natural sources, iron and steel production, cement production and related activities, nonferrous metals production, and municipal solid waste incinera- tion [1]. Cadmium is one of six substances banned by the European Union’s Restriction on Hazardous Substances (RoHS) directive, which bans certain hazardous substances in electrical and elec- tronic equipment but allows for certain exemptions and exclusions from the scope of the law [2]. Bread, root crops, and vegetables also contribute to the cadmium in modern populations [3]. Long-term exposure to cadmium in contaminated food and water has resulted in a few instances of general population toxicity, and researches are ongoing regarding the estrogen mimicry that may induce breast cancer [3]. Concisely, for all of the mentioned reasons, the cadmium (II) like many chemical elements is extremely harmful to human and other living organism health. ∗ Corresponding author. Tel.: +98 25 38745629. E-mail address: Soleyman.ramezani@yahoo.com (S. Ramezani). So, it is worthy to expand an accurate, rapid and sensitive method to monitor Cd (II) concentration in the environmental sam- ples. For this purpose, many instrumental methods such as atomic absorption spectrometry (AAS) [4], inductively coupled plasma mass spectrometry (ICP-MS) [5], and atomic fluorescence spec- trometry (AFS) [6] have been used. Although these techniques have good selectivity and high sensitivity, they are somewhat time-consuming, expensive and not convenient for the in situ measurement. On the contrary, the electrochemical techniques for determination of trace metals have attracted increasing interests due to their high sensitivity, rapid performance, portability, low cost and the simple instrumentation. Because of the toxicity of mer- cury and the feasibility of formation of intermetallic compounds in amalgams, numerous new electrode materials and methods are desired to replace it. At present, several mercury-free electrodes, such as bismuth film electrodes [7], carbon nanotube modified electrodes [8], nano-porous pseudo carbon paste electrodes (nano- PPCPEs) [9,10], acetylene black electrode [11], lead film electrode [12], boron-doped diamond electrode [13], nano-TiO 2 /chitosan combination film [14] and carbon paste electrodes [15] are devel- oped for sensitive electrochemical determination of diverse metals ion in various aqueous and non-aqueous media. Among them, chemically modified carbon paste electrodes (CMCPEs) have seized 0925-4005/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.snb.2013.11.033