Potentiometric Sensing of Ions in Environmental and Biological Samples

Potentiometric sensing employs the measurement of an electrical potential difference between an ion‐selective electrode and a reference electrode to determine the activity of specific ions in complex matrices. Over recent decades, advances in ionophore chemistry, solid‐contact transducer materials and miniaturised fabrication techniques have transformed these sensors from laboratory curiosities into robust tools for in situ monitoring. In environmental science, potentiometric sensors are deployed for continuous assessment of pH, nutrient cycles (nitrate, ammonium, phosphate), trace metals and emerging contaminants in freshwater, seawater and soils. In the biomedical arena, wearable and implantable solid‐state electrodes enable real‐time tracking of electrolytes in sweat, interstitial fluid and blood, offering new insights into hydration, metabolic disorders and drug monitoring. Key challenges in the field include ensuring high selectivity in the presence of interfering species, suppressing potential drift over extended deployments and preventing biofouling in biological fluids. The integration of conducting polymers, carbon‐based and two‐dimensional nanomaterials as solid contacts has yielded sensors with enhanced stability, rapid response and Nernstian behaviour, while additive manufacturing and microfluidic integration have paved the way for portable, user‐friendly devices with global applications in environmental stewardship and personalised healthcare.

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Potentiometric Sensing of Ions in Environmental and Biological Samples publication trend

The graph below shows the total number of articles in potentiometric sensing of ions in environmental and biological samples across all publications each year (not limited to Nature Index journals).

Technical terms

Potentiometry: An electrochemical technique in which the potential difference between an indicator electrode and a reference electrode is measured to quantify ion activity.

Ion-Selective Electrode (ISE): A sensor consisting of a selective membrane that generates a potential proportional to the activity of a target ion in solution.

Ionophore: A membrane-bound receptor molecule that selectively binds a specific ion, imparting sensor selectivity.

Solid Contact: An ion-to-electron transducer layer that replaces the internal liquid junction, enabling all-solid-state ISEs with enhanced mechanical robustness.

Nernstian Response: The theoretical relationship whereby electrode potential changes by 59.16 mV per tenfold change in ion activity at 25 °C.

References

1. Advancing Multi‐Ion Sensing with Poly‐Octylthiophene: 3D‐Printed Milker‐Implantable Microfluidic Device. Advanced Science (2024).
2. MXene-Coated Ion-Selective Electrode Sensors for Highly Stable and Selective Lithium Dynamics Monitoring. Environmental Science and Technology (2023).
3. Electrochemical sensors for in-situ measurement of ions in seawater. Sensors and Actuators B Chemical (2021).
4. Solid-Contact Ion-Selective Electrodes: Response Mechanisms, Transducer Materials and Wearable Sensors. Membranes (2020).
5. All-solid-state potentiometric sensors: A new wave for in situ aquatic research. Current Opinion in Electrochemistry (2018).