Water quality is a key indicator of environmental pollution and is a critical measurement in the water industry. It is essential to be able to detect water contamination quickly. Traditional ion sensors for detecting contaminants in water are affordable and simple to use but have slow response times and thermodynamically limited sensitivities.

Continuous, real-time sensing of ions is of great value across various environmental and medical organisations, but remains underdeveloped. In response to this need, researchers at the University of Oxford have developed a sensor for continuous ion sensing under flow.

Oxford technology

The technique involves the use of continuous and polarisation-tuned redox capacitive sensing at suitably designed electroactive interfaces. The redox activity of these electroactive receptive interface can be accurately measured by redox capacitance spectroscopy, affording analogous information to that typically resolved by known voltammetric methods.

The presence of an ion binding to the electroactive interface changes the ratio of oxidised/reduced receptor states. This change in ratio is directly dependent on the so called redox density of states (DOS).

The researchers have found that by monitoring the shift by redox capacitance DOS measurements (rather than voltammetrically) provides advantages:

• Continuous monitoring of under flow
• Used with a broad range of specific surface potentails
• It can create a simple, direct readout
• It can produce higher sensitivity
• Improved temporal resolution

All of the advantages allow for live measurements of flowing water to be monitored.

There is no need to take sample volumes from the water source, so less infrastructure is required for implementation.

Opportunity

This technology can be used to sense any analyte that can reversibly peturb the voltametric profile of the electroactive interface (including anions, cations, and neutrally charged molecules and atoms).