Stripping Voltammetry on a new Modified Glassy Carbon Electrode for Lead Content Determination in Soft Water

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.