Electrochemical detection of per- and polyfluoroalkyl substances: A review

Abstract

Per- and poly-fluoroalkyl substances (PFASs) are recognised for their environmental persistence and bioaccumulation, necessitating a dependable detection technology. Traditional methods examine multiple facets. Electrochemical sensors represent a preferable alternative due to their reliability, real-time detection capabilities, and potential for on-site analysis. Metal-organic frameworks (MOFs) and molecularly imprinted polymers (MIPs) exhibit remarkable properties in analysis, including high sensitivity and selectivity, rapid response and efficient electron transfer capabilities. Nonetheless, the stability of MOFs occasionally poses issues in aquatic conditions. Utilising a microfluidic channel between interdigitated microelectrodes (IDμE) in a MOF-based electrochemical sensor for PFASa detection offers numerous advantages. It possesses a minimal limit of detection (LOD), comparable to cutting-edge ex-situ methodologies. The molecular interactions of the capture probes provide effective electrochemical transduction, while the nanoporous morphology of the materials and IDμE significantly enhance the signal-to-noise ratio. Extended diffusion durations impede detection abilities and limit molecular interactions between PFAS and electrode surfaces. The selectivity challenges involve differentiation problems and complex matrices. Accurately identifying PFAS compounds in samples is problematic, especially those with similar carbon chain lengths, and existing sensors are hindered by interference from non-fluorinated surfactants. Improvements in electrode design can be realised by the use of nonplanar interdigitated microelectrode arrays (NP-IDμE), the application of nanoporous and capacitive electrode technologies, and the incorporation of electrode nano-porosity to minimise non-specific adsorption. Improvements in signal and sensitivity can optimise the detection process. Signal increases can be attained by decoupling sensitivity and selectivity using force as a tuning parameter, employing ambient oxygen as a mediator molecule instead of expensive ferrocene, and utilising electrochemical impedance spectroscopy (EIS) for improved sensitivity. Integrating IoT with EC PFAS sensors indicates a promising future for environmental monitoring.