Measuring Open Circuit Potential (OCP) Using the SenseItAll Potentiostat

Open Circuit Potentiometry (OCP), sometimes referred to as Open Circuit Potential measurement, is one of the simplest electrochemical techniques available. Unlike voltammetric methods where a potential is applied to drive electrochemical reactions, OCP measures the natural potential that develops between electrodes when no external current is flowing.

In this article, we demonstrate how to measure the open circuit potential of a ferricyanide solution using the SenseItAll Potentiostat, a Carbon 501 Screen-Printed Electrode (SPE), and only 50 µL of sample.

What is Open Circuit Potentiometry?

Open Circuit Potentiometry measures the equilibrium potential of an electrochemical system under zero-current conditions.

In simple terms, the potentiostat observes the voltage naturally generated by the electrochemical system without disturbing it.

Because no significant current flows during the measurement, OCP is commonly used for:

✅ Sensor evaluation
✅ Reference electrode assessment
✅ Chemical equilibrium studies
✅ Corrosion monitoring
✅ Electrochemical characterisation
✅ Teaching electrochemistry fundamentals

OCP is often one of the first measurements performed before more advanced electrochemical techniques such as cyclic voltammetry or chronoamperometry.

Why Measure Ferricyanide?

Ferricyanide is one of the most widely used electrochemical standards because of its well-defined and reproducible redox properties.

The ferricyanide/ferrocyanide redox couple:

Fe(CN)6³⁻ + e⁻ ⇌ Fe(CN)6⁴⁻

provides a stable and predictable electrochemical system that is ideal for demonstrating electrochemical techniques.

For this experiment we use:

🧪 Potassium Hexacyanoferrate (Ferricyanide) Solution
https://shop.zimmerpeacock.com/en-gb/products/potassium-hexacyanoferrate-solution

Experimental Hardware

The experiment uses:

📱 SenseItAll Potentiostat
https://shop.zimmerpeacock.com/en-gb/products/senseitall-sia-generation-4-device-only

⚡ Carbon 501 Sensor Cartridge Pack
https://shop.zimmerpeacock.com/en-gb/products/carbon-501-sensor-cartridge-pack

🔬 Screen-Printed Electrodes Collection
https://shop.zimmerpeacock.com/en-gb/collections/bare-electrodes

🧫 Electrochemistry Solutions & Accessories
https://shop.zimmerpeacock.com/en-gb/collections/solutions

One of the most distinctive features of the SenseItAll platform is its cartridge-based electrode system.

Rather than connecting individual electrodes with clips and leads, the cartridge simply slots into the potentiostat and clicks into place.

This design is particularly useful for:

Teaching laboratories
Undergraduate practical classes
Sensor development
Commercial product development
Electrochemical research

Small Sample Volumes, Big Advantages

After inserting the electrode cartridge into the potentiostat, only 50 µL of ferricyanide solution is applied to the electrode surface.

Using such small sample volumes offers several practical advantages:

Reduced reagent consumption
Lower operating costs
Less chemical waste
Simplified disposal
Greater throughput for teaching laboratories

For institutions training large numbers of students, this can significantly reduce laboratory costs while maintaining a hands-on electrochemistry experience.

Configuring the OCP Experiment

The experiment is performed using SenseItAll Desktop.

The following setup was used:

Parameter	Value
Technique	Open Circuit Potentiometry (OCP)
Runtime	30 seconds
Save Rate	1 point per second
Sample Volume	50 µL

Once the experiment is configured, the measurement begins immediately.

Because no potential is applied, the software simply records the natural electrochemical potential generated by the system over time.

Understanding the OCP Measurement

During the experiment, the measured potential was observed to stabilise around approximately:

300 mV

While small changes occurred during the 30-second experiment, the overall response remained relatively stable.

This stability is important because it indicates:

A well-behaved electrochemical system
Good electrode performance
Effective electrical contact
Repeatable electrochemical conditions

When viewed on the graph, the signal may appear to drift slightly, but when considered relative to the overall voltage scale, the variation is relatively small.

This provides an excellent teaching example of equilibrium electrochemistry.

Why OCP is Important

Although Open Circuit Potentiometry is one of the simplest electrochemical techniques, it provides valuable information.

Researchers frequently use OCP measurements to:

Assess electrode stability
Monitor equilibration processes
Evaluate sensor performance
Characterise chemical systems
Establish baseline conditions before voltammetry

In many electrochemical workflows, OCP is the starting point that informs subsequent measurements.

An Excellent Teaching Demonstration

One of the strongest features of this experiment is its simplicity.

Students can:

Insert the sensor cartridge.
Apply 50 µL of solution.
Select Open Circuit Potentiometry.
Start the measurement.
Observe the potential stabilisation process.

This enables learners to focus on understanding electrochemical behaviour rather than spending time assembling complex instrumentation.

The minimal chemical usage also makes the experiment highly practical for teaching laboratories.

Automatic Cloud Data Storage

After the measurement has been completed, the data is automatically uploaded to the cloud using the Djuli platform.

☁️ Djuli Cloud Platform
https://djuli.zimmerpeacock.no/

Benefits include:

Automatic backups
Easy experiment retrieval
Centralised storage
Reduced risk of data loss
Improved collaboration

This modern workflow helps answer a common laboratory question:

"Where is my data?"

With automatic cloud storage, the answer is simple.

Beyond Open Circuit Potentiometry

The SenseItAll platform supports a wide range of electrochemical techniques including:

Cyclic Voltammetry (CV)
Square Wave Voltammetry (SWV)
Linear Sweep Voltammetry (LSV)
Chronoamperometry (CA)
Open Circuit Potentiometry (OCP)

The same hardware platform can therefore be used throughout electrochemistry courses, research projects, and commercial development programmes.

In addition, measurements can be performed through:

SenseItAll Desktop
iPhone devices
Android devices

providing significant flexibility for users.

Products Used

📱 SenseItAll Potentiostat
https://shop.zimmerpeacock.com/en-gb/products/senseitall-sia-generation-4-device-only

🧪 Potassium Hexacyanoferrate (Ferricyanide) Solution
https://shop.zimmerpeacock.com/en-gb/products/potassium-hexacyanoferrate-solution

⚡ Carbon 501 Sensor Cartridge Pack
https://shop.zimmerpeacock.com/en-gb/products/carbon-501-sensor-cartridge-pack

🔬 Screen-Printed Electrodes Collection
https://shop.zimmerpeacock.com/en-gb/collections/bare-electrodes

🧫 Electrochemistry Solutions & Accessories
https://shop.zimmerpeacock.com/en-gb/collections/solutions

Conclusion

Open Circuit Potentiometry is one of the simplest yet most valuable electrochemical measurements. Using the SenseItAll Potentiostat and a Carbon 501 screen-printed electrode, stable OCP measurements can be collected using only 50 µL of ferricyanide solution.

The ease of setup, low chemical consumption, automatic cloud storage, and educational value make this an excellent experiment for teaching laboratories, research groups, and commercial electrochemical development projects.

Learn More

If you have any questions about Open Circuit Potentiometry, electrochemical sensors, screen-printed electrodes, or the SenseItAll platform, we'd be delighted to help.

📩 Contact Zimmer & Peacock:
https://www.zimmerpeacock.com/contact