Enhanced Electrochemical Detection of Multiheavy Metal Ions Using a Biopolymer-Coated Planar Carbon Electrode

In this paper, a chitosan biopolymer-coated planar carbon electrode was developed for in situ determination of heavy metals (Zn²⁺ and Pb²⁺) using square-wave anodic stripping voltammetry. The experimental conditions were optimized with respect to deposition time, amplitude, and frequency. With 300-s deposition time, the heavy metal stripping was conducted at 0.05-V pulse amplitude, 20-Hz pulse frequency, and 0.004-V square-wave step voltage in 0.1-M acetate buffer at pH 4.6. Two distinguished peaks were observed at -0.86 and -0.37 V, which are associated with the stripping of Zn²⁺ and Pb²⁺, respectively. The limit of detection was 0.6 and 1 ppb for Zn²⁺ and Pb²⁺, respectively, and the relative standard deviations for repetitive measurements of Zn²⁺ and Pb²⁺ were in the range of 4.8%-5.4% (n = 30 with two identical electrodes). The chitosan biopolymer-coated carbon electrode was successfully applied for detecting Pb²⁺ in tap water, mining wastewater, and soil leachate, and showed a reliable performance for measuring heavy metals with acceptable reproducibility. Overall, the developed biopolymer-coated carbon electrode exhibited excellent representativeness and reproductivity for in situ multiheavy metal ions detection in spiked samples, holding a great promise for on-site testing of heavy metals in drinking water.

I. Introduction

Water and soil contamination by heavy metals has gained much attention due to its significant impact on public health. Heavy metal ions (e.g., zinc, copper, cadmium, and lead) are used in several industrial applications and are recognized as agents that present various toxic effects to humans, animals, and other living organisms. These metals are well-known water pollutants, which are not biodegradable, and have long biological half-lives; hence, they tend to bioaccumulate in higher trophic levels of the food chain. Due to growing rigorous environmental regulations, the legal limits for heavy metals in drinking water (e.g., 5 ppm of zinc [Zn²⁺] and 0.015 ppm of lead [Pb²⁺]) are becoming stricter [1]. Particularly, Pb²⁺ leaching from galvanic corrosion and elevation of lead levels in household plumbing systems have increasingly drawn public attention [2]. The lead in drinking water has been regulated by Lead and Copper Rule (LCR) with the permissible Pb²⁺ concentration less than 15 ppb [3], and thus, fast and simple detection of lead in drinking water is imperative for public health.