This paper focuses on electrochemical characterization of new azulene compound 2,6-bis((E)-2-(thiophen-3-yl)vinyl)-4-(4,6,8-trimethylazulen-1-yl)pyrylium (L) by cyclic voltammetry (CV), differential pulse voltammetry (DPV), rotating disk electrode voltammetry (RDE) on glassy carbon disk working electrodes. The character of redox processes was established by CV and RDE using increasing scan rates at different scan domains. PolyL modified electrodes have been prepared by scanning or controlled potential electrolysis (CPE). The complexing properties of L and polyL have been investigated towards detection of heavy metal ions by anodic stripping technique. The voltammetric curves present well defined peaks for Pb2+, Cd2+, Cu2+ and Hg2+, which can be used as analytical signals for their determination. The performances of the modified electrodes obtained at different potentials and charges have been evaluated. The best results have been obtained for Pb2+ and Cd2+ with the achievement of detection limits of 10-7 M.
This study develops a new electrochemical method for quantification of Pb in soft water using stripping voltammetry with a glassy carbon electrode modified with the functionalized azulene: (2E)-2-(azulen-1-ylmethylidene) hydrazine carbothioamide (L) as a complexing polymer film. The optimized steps of the proposed method consisted in experimental establishing of four parameters, namely: reduction time; reduction potential; complexation time; pH in acetate buffer and phosphate buffer. The modified electrodes were prepared in L solutions (1mM) in acetonitrile (CH3CN) containing tetra n-butyl ammonium perchlorate (0.1 M TBAP) as supporting electrolyte. The electrochemical method includes four main operations: 1) polymeric film formation by controlled potential electrolysis (CPE) at 1.7V using a charge of 1 mC; 2) film conditioning in 0.1 M buffer acetate solution using cyclic voltammetry; 3) 25 min complexation time in a standard solution prepared from lead nitrate (II) using as matrix ultrapure water or a real sample; 4) stripping by differential pulse voltammetry method (DPV) in acetate buffer at pH 4.0, after 120 s reduction time at a reduction potential of -1.0 V. Determination time for a single standard solution or real sample was around 45 min. Evaluation of the method performance parameters (linearity, working range, detection limit, quantification limit, repeatability, and recovery) was done. It confirms that the proposed method is suitable to detect and quantify lead content over 1.2 �g/L in soft water samples.
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