Detection of Cadmium, Lead and Mercury Ions by a Chemically Modified Carbon Paste Electrode with Schiff Base Using Square-wave Anodic Stripping Voltammetry

Abstract

Purpose: A modified carbon paste electrode (CPE) was developed to determine the content of cadmium (Cd²⁺),
lead (Pb²⁺) and mercury (Hg²⁺) ions in aqueous solutions.
Methods: The CPE was modified using the Schiff base of 2-hydroxy-5-nitrobenzaldehyde with S-benzyldithiocarbazate. The performance of modified and unmodified electrodes were compared. Several important
parameters controlling the performance of the modified electrode were optimized using square-wave anodic stripping voltammetry (SWASV). The electrochemical behavior of the modified electrode was characterized by cyclic
voltammetry.
Results: The modified electrode exhibited good selectivity, stability and reproducibility. Under optimized conditions, calibration curves demonstrated linearity over a concentration range of 25 – 1000 ng mL^-1 for Cd²⁺ and
Hg²⁺; and 25 – 2500 ng mL^-1 for Pb²⁺ using a deposition time of 70 s. The limits of detection for Cd²⁺, Pb²⁺
and Hg²⁺ were 9.50, 17.09 and 13.16 ng mL^-1, respectively. Simultaneous determination of Cd²⁺, Pb²⁺ and
Hg²⁺ was performed and no interference was observed.
Conclusion: The modified electrode was successfully used to determine the content of Cd²⁺, Pb²⁺ and Hg²⁺
in river water samples, giving results that agreed well with those obtained by atomic absorption spectrometry
(AAS).