Impact of physical and chemical parameters on square wave anodic stripping voltammetry for trace Pb2+ detection in water

Abstract

Exposure to lead, a toxic heavy metal, in drinking water is a worldwide problem. Lead leaching from lead service lines, the main contamination source, and other plumbing materials is controlled by the plumbosolvency of water. Square wave anodic stripping voltammetry (SWASV) has been greatly explored as a rapid and portable technique for the detection of trace Pb²⁺ ions in drinking water. However, the impact of water quality parameters (WQP) on the SWASV technique is not well understood. Herein, SWASV was employed to detect 10 μg L⁻¹ Pb²⁺ and determine trends in the stripping peak changes in simulated water samples while individually varying the pH, conductivity, alkalinity, free chlorine, temperature, and copper levels. The pH and conductivity were controlled using the buffer 3-(N-morpholino)propanesulfonic acid (MOPS), and NaNO₃, respectively and kept at pH = 7.0 and conductivity = 500 μS cm⁻¹ when exploring other WQPs. The working electrode, a gold-nanoparticle-modified carbon nanotube fiber cross-section (AuNP-CNTf-CS) electrode provided sufficiently sharp and prominent peaks for 10 μg L⁻¹ Pb²⁺ detection as well as good reproducibility, with a relative error of 5.9% in simulated water. We found that conductivity, and temperature had a proportional relationship to the peak height, and pH, alkalinity, free chlorine, and copper had an inverse relationship. In addition, increasing the copper concentration caused broadening and shifting of the Pb²⁺ stripping peak. At extremely low conductivities (<100 μS cm⁻¹), the voltammograms became difficult to interpret owing to the formation of inverted and distorted peaks. These trends were then also observed within a local drinking water sample in order to validate the results.