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Article Prepared By: Izwaharyanie Ibrahim
Source: Current Opinion in Electrochemistry (Elsevier)
The detection of per- and polyfluoroalkyl substances (PFAS) in the environment has become a critical public health and environmental issue. PFAS, known for their persistence and resistance to degradation, have become nearly ubiquitous in surface water, drinking water, and biological samples. Electrochemical sensors offer an affordable and portable solution to detect PFAS on-site. However, one major variable remains underexplored: time.
In their 2025 review article, Cullom and Dick argue that temporal control and analysis in electrochemical PFAS sensing can significantly enhance sensitivity, specificity, and interpretability [1]. They emphasize that most studies report only the final signal values, often ignoring how those signals evolve over time [2].
Why Time Matters
PFAS are non-electroactive, meaning they don't easily undergo oxidation or reduction. As such, sensors rely on indirect detection—typically through signal changes in redox probes or materials [3]. The rate at which these signals change (e.g., during accumulation, binding, or desorption) carries valuable information.
For example, monitoring the kinetics of PFAS adsorption onto sensor surfaces can help differentiate between long-chain and short-chain PFAS [4]. Similarly, real-time tracking of signal drift may expose surface fouling or sensor degradation, allowing more accurate calibration [5].
Figure 1- a) The molecular structure of PFOS. b) The molecular structure of PFOA c) Sum of concentration of 20 PFAS subject to EU guidance in surface water, groundwater and drinking water samples. Those above the EU drinking water limit of 100 ng l−1 (marked red on scale bar) are circled in red (for known contamination sources (for example, AFFF or non-AFFF)) or black (unknown sources). Note the scale bar is a logarithmic scale.
Techniques That Benefit from Time Integration
Electrochemical Impedance Spectroscopy (EIS) is one such technique that inherently involves time, yet most analyses focus only on frequency-domain outputs [6]. Cullom and Dick suggest that time-resolved EIS could yield insights into PFAS adsorption rates and sensor stability [7].
Chronoamperometry and chronopotentiometry, which directly record current or voltage over time, are powerful but underused in PFAS research [8,9]. The authors highlight that introducing delay periods during these techniques may help segregate fast vs. slow binding events, improving selectivity [10].
Figure 2- Different types of common electrochemical sensors. a) Enzyme biosensors can react with a target molecule and create an electrical signal or may need a mediator to create the electrical signal for detection. b) Antibody sensors often have multiple layers to detect and electrochemically react to an analyte. c) Aptamer sensors will bind to an analyte, then undergo a conformation change. This conformation change will alter the current detected at the electrode. d) Molecularly Imprinted Polymers (MIPs) are polymers built around a template molecule. The template gets extracted, leaving holes that are selective to the analyte behind. Analytes and small molecules will enter those holes and a decrease in current is detected.
Time as a Tool for Selectivity and Validation
Time-resolved approaches can:
By integrating time into sensor design and analysis, researchers can improve robustness, reproducibility, and ultimately, real-world usability of electrochemical PFAS sensors [14].
Current Gaps in Practice
Despite its promise, time is rarely treated as a variable in PFAS sensor literature. Most studies lack:
The paper calls for better reporting standards—such as including time-course graphs and explicitly stating experimental timeframes [19]. It also encourages journals and funding bodies to recognize time-based analysis as a valid, impactful innovation [20].
A Way Forward for Malaysia
As PFAS detection becomes increasingly important in Malaysia’s water policy and pollution control strategies, I-AQUAS sees time-aware sensor development as a frontier worth exploring. Our future work may incorporate time-domain signal tracking into in-house developed PFAS biosensors, especially for aquaculture and river basin monitoring.
References
Date of Input: 01/08/2025 | Updated: 11/11/2025 | m_fakhrulddin
