Design and characterization an electrochemical flow sensor based on the CNT-conducting polymer composite for the selective determination of Cr (VI) in the presence of Cr (III)

Environmental pollutants, especially heavy metals, are now the global warning giving threats to the humanity. Chromium ions are one of the most common toxic ions contained in industrial waste water [1]. The most prominent example of toxic chromium is hexavalent chromium. The toxicity of Cr (VI) is due to its strong oxidational properties and easy permeation of biological membranes [2]. As it would be dangerous even in trace amount, the accurate trace determination of these heavy metals is important. Up to now, various approaches have been established for the determination of Cr (VI). In the recent years rapid analytical methods have been developed through the initiation of various generations of flow injection analysis (FIA) [3].Here, a new and selective electrochemical flow sensor was developed for selective determination of Cr (VI) in presence of Cr (III) by flow injection analysis with amperometric detection.The glassy carbon electrode (GCE) was modified by drop casting of multiwall carbon nanotube (MWCNT) suspension. After drying of the electrode surface at room temperature, the surface was subsequently modified with a thin film of poly methylene blue (PMB) by cyclic voltammetry. The constructed modified electrode showed better electrochemical response in comparison with bare GCE and GCE modified by polymer.All effective chemical and instrumental variables were optimized. Under the optimum conditions, results indicated an excellent linearity between FIA response and (VI) concentration in the range of 0.3-35 µM with correlation coefficient 0.9976. The detection limit of 0.07 µM was found. The accuracy and precision of method was studied by analyzing of synthetic standard samples.