Detection of Perchlorate in Swabs Using Linear Sweep Voltammetry at a Liquid–Liquid Microinterface Array

Abstract

Perchlorate is a potential environmental contaminant and ease of its detection is needed to support environmental monitoring. Current detection methods mainly involve chromatographic and mass spectrometric methods, which have limitations in terms of portability and cost. This study explores the use of electrochemistry at the interface between two immiscible electrolyte solutions (ITIES) as an approach for perchlorate detection within sample swabs, e.g., from plant leaf surfaces in areas which may be contaminated with debris from frequent firework displays. Ion transfer voltammetry was employed to detect perchlorate based on its transfer across an array of micrometer-scale ITIES (µITIES). Experiments to evaluate sensitivity and selectivity of the approach enabled detection of less than 1 μM of perchlorate; the presence of common additional ions, such as nitrate, hydrogen phosphate, and sulfate, did not impact the detection of perchlorate. A series of experiments in which perchlorate was intentionally introduced into samples, both on cotton swabs and on leaf surfaces that were subsequently swabbed, showed that cotton swabs could be used to sample perchlorate from environmental surfaces. Field sampling of leaf surface before and after firework displays indicates that ion transfer voltammetry at a µITIES array offers a viable approach to the detection of perchlorate in swabs and on swabbed surfaces.