How to care for pH electrodes

Ongoing maintenance and care of pH electrodes is integral for achieving accurate results on every test. Taking the time to learn and follow the best practices for electrodes of all types helps to ensure reliability in readings, whether measuring water or soil out in the field or testing using a benchtop pH meter in a laboratory. Read on to learn how to care for pH electrodes effectively: 

Why is following best practices for pH electrodes important?

Best practices are a series of rules and processes to follow to maintain your pH electrode for testing. By following these steps, you can improve the longevity of your electrode and ensure your pH measurements are accurate with each test. Not following best practices can lead to your electrode becoming damaged over time, resulting in inaccuracy and reducing the electrode’s lifespan.

For more detailed instructions on caring for your specific pH electrode, see the instruction manual packaged with your electrode, tester or meter. Manuals are also available online through our website for easy access.

Best practice for maintaining pH electrodes

Maintain hydration

Hydration is vital for the longevity and accuracy of pH electrodes. A dry electrode can have erratic readings, difficulty stabilising, pH drift, slow response times, and may provide inaccurate pH measurements. You can rehydrate a dried-out electrode by submerging both the bulb and junction into a pH storage solution.

Store in a suitable storage solution

Suitable storage helps to maintain pH electrodes in the long term. While you may want to use deionised water for storage, this causes the ions to leach from the reference electrolyte and the glass membrane, damaging the electrode and leading to slow response times and inaccurate measurements due to contamination of the reference electrode. Using a pH storage solution is the best option for your electrode. If you currently have none to hand, pH 4.01 buffer can be used as a temporary alternative, as it is the most similar in consistency to the storage solution and reference electrode.

Regularly inspect your electrode

Scratches and damage from use can occur over time with electrodes, alongside general signs of ageing. Regularly checking your electrode can provide an early warning sign that your electrode needs to be replaced soon. You can also perform a slope and offset calculation, as detailed in our free PDF download, to ensure your electrode is working properly.

Submerge your electrode correctly

Both the reference junction and the pH sensing glass of the electrode need to be fully immersed in your sample to function correctly and achieve accurate readings. Increasing your sample volume for sufficient coverage ensures measurement accuracy. In situations where samples are always smaller than the recommended volume, you can use a narrower diameter vessel and a specialist electrode.

Keep the electrolyte level topped up

For refillable electrodes, it’s important to keep track of the level of electrolyte over time. As electrolyte flows out from the reference function with use, it needs to be replaced up to a suitable level to prevent erratic readings. Make sure your electrolyte fill level is within 0.5 inches or 12.5mm of the fill hole cap for best results.

Choose the right electrode for your sample

Using the correct electrode for the type of sample you are measuring can help to ensure accuracy, achieving the best possible precision for the specific material you’d like to measure. For example, a clog-resistant electrode is the best choice for specific food products, while a low-temperature electrode is more applicable for certain samples. 

If you need to measure a specific type of sample repeatedly, picking the right electrode is the best way to achieve long-term accuracy. Contact our team directly to discuss your requirements, and we will help you find the best electrode for your application.

Rinse, don’t wipe

Wiping the glass of pH electrodes with a towel or cloth can produce a static charge, interfering with pH readings. Instead, rinse electrodes with distilled or deionised water to remove traces of samples, ready for the next measurement. 

If you are using an electrode arm, you can tap the arm to remove the excess moisture or allow it to air-dry. If you are not using an arm, you can blot with a lint-free cloth before use. You can also use cleaning solution sachets to help remove stubborn materials from electrodes, rinsing with DI water after to remove any residue left on the electrode.

Clean regularly

Over time, deposits from samples can leave a film on the electrode, even if this is not visible to the eye. This can cause calibrations to be ineffective and result in incorrect pH readings. Using a specialist cleaning solution for your specific sample, such as soil or cheese cleaning solution, helps to remove that film and maintain the accuracy of your pH electrode.

Open or loosen the fill hole cap

If you have a refillable electrode, you may find that a closed fill hole leads to problems with stabilisation times. Loosening or removing the cap on the fill hole can be an effective way to resolve this issue. The cap must be replaced properly before you store the electrode after measurement.

Calibrate frequently

Calibration is key to achieving consistent, long-term accuracy with pH electrodes. The frequency of calibration will depend on your specific requirements, industry standards and the degree of accuracy necessary when measuring pH. It is recommended to choose pH buffer solutions that bracket the expected pH of the sample for best accuracy within that specific pH range.

Calibrating often with Hanna calibration solutions helps your pH electrode to be as precise as possible over its lifespan. The pH instrument should be recalibrated in these circumstances:

1. When the pH electrode is replaced
2. After testing aggressive chemicals
3. Where a high degree of accuracy is required
4. Once monthly, or before use if stored or unused for longer than a month

If you conduct multiple tests daily or work in an industry where a high degree of accuracy is required, calibrating daily or weekly may be more suitable for your requirements. Speak to our team directly for personalised advice on calibration for your application.

Buy pH electrodes and solutions today

Hanna stocks a wide range of general and specialist pH electrodes for many industries, from laboratories to food, agriculture or water testing. 

We also stock all required cleaning, calibration and storage solutions to keep your electrode in good condition, with all in-stock products available for next-day delivery with free shipping on orders over £50. Shop pH electrodes and solutions online now.

Need advice on the best pH meters, testers or electrodes for your application? Contact our experts directly for personalised recommendations. Call 01525 850 855 or email us at sales@hannainstruments.co.uk today.