The toxicity of metals such as lead (Pb), cadmium (Cd), arsenic (As), and copper (Cu) has been a worldwide issue since the 1970s. For Pb specifically, there have been a number of communities in the United States where children have been exposed to elevated concentrations in drinking water. This can have lasting negative effects. While inductively coupled plasma-mass spectrometry (ICP-MS) and atomic absorption spectroscopy (AAS) are the most common instruments used for detection of Pb2+, electrochemical methods have also shown promise. Square wave anodic stripping voltammetry (SWASV) has been successfully applied for this purpose and has proven to be highly sensitive and selective for Pb2+ analysis. However, the determination of metals in a real sample matrix typically requires pre-treatment and/or extraction of the analyte from the sample itself. Cloud point extraction (CPE) is a sustainable technique originally implemented for the preconcentration of metals but has been adapted for a variety of organic analytes as well. CPE can be used as a solvent-less substitute for liquid-liquid or solid-phase extraction and has traditionally been coupled to detection systems such as AAS. Its applicability to electroanalysis, though, is not well understood. There have been two publications of CPE used in tandem with electrochemical techniques, neither of which included a back-extraction step to decrease matrix effects in the final sample for analysis. In this work, CPE was used to isolate Pb2+ from water samples for analysis by SWASV with a bismuth-coated glassy carbon (Bi-GC) electrode. A back-extraction (BE) step was utilized to remove residual surfactant and it resulted in a more sensitive, long-lasting Bi-GC electrode for Pb2+ detection. Excellent extraction efficiency was achieved as the preconcentration factor was determined to be 10 or better (verified by AAS). Theoretical limits of detection (LODs) of 0.74, 0.58, and 0.38 ppb were obtained for deposition times of 1, 2, and 3 min, respectively. While the LOD was lower with longer deposition time, the response was more variable from trial-trial. Lastly, the CPE-SWASV procedure for Pb2+ was quite selective; only manganese (Mn2+) and Cu2+ were identified as possible interferants. Measurements in tap and environmental water samples were also completed. Overall, this novel approach of coupling SWASV to CPE provides a sensitive, cost-effective, and sustainable method for the quantification of Pb2+.

Cloud point extraction for the determination of lead with a bismuth-film glassy carbon electrode by anodic stripping voltammetry

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.