Hanna Instruments has put together a guide to serve as a quick reference for best practices. Accurate pH measurements depend as much on how you treat your electrode as on the instrument itself. Poor storage, incorrect rinsing, or irregular calibration are among the most common causes of drifting readings and premature electrode failure. This guide, compiled by Hanna Instruments, covers the ten most important practices to keep your electrode performing at its best.
1. Keep the electrode hydrated
- Why: Drying out the electrode leads to drifting pH values, slow response times, and incorrect measurements.
- Fix: Revive a dry electrode by submerging the bulb and junction in pH storage solution for at least one hour.
2. Store your electrode in storage solution
- Why: Storing in deionised water (DI) causes ions to leach from the glass membrane and reference electrolyte, resulting in a slow and sluggish response.
- Fix: Store in a dedicated storage solution, or use pH 4.01 or pH 7.01 buffer if storage solution is unavailable.
3. Rinse, do not wipe your electrode
- Why: Wiping the pH glass can produce a static charge that interferes with the pH reading.
- Fix: Rinse with distilled or deionised water. Blot (do not rub) with a lint-free paper towel (e.g. Kimwipes) to remove excess moisture.
4. Clean your electrode regularly
- Why: Deposits can form on the electrode during use, coating the sensing glass and leading to erroneous calibrations and readings.
- Fix: Clean using a specially formulated cleaning solution for pH electrodes — ideally one developed for your specific application.
5. Calibrate often
- Why: All pH electrodes need to be calibrated regularly for best accuracy.
- Fix: Calibration frequency depends on required accuracy — daily calibration is ideal.
6. Pick the right electrode for your sample
- Why: General purpose electrodes work for many applications but are not ideal for all samples.
- Fix: Depending on your sample, you may need an electrode designed for food, high/low temperature, non-aqueous, or other specific sample types.
7. Open or loosen the fill hole cap
- Why: A closed fill hole may lead to lower stabilisation times.
- Fix: Loosen or remove the fill hole cap during use. Replace it when storing the electrode. (Not applicable for non-refillable electrodes.)
8. Keep the electrolyte level full
- Why: Electrolyte flows out from the reference junction over time. Low levels may cause erratic readings.
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Fix: Ensure the fill solution level is no less than one-half inch from the fill hole cap.
(Not applicable for non-refillable electrodes.)
9. Properly submerge your electrode
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Why: Both the pH sensing glass and reference junction must be completely immersed to function properly.
- Fix: Add enough sample to submerge both the junction and the sensing glass before taking a reading.
10. Inspect your electrode
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Why: Over time the sensing glass becomes less responsive and will eventually fail. Physical damage from use can also cause erroneous readings.
- Fix: Check regularly for visible damage and perform a slope and offset calculation to verify performance.
Always consult the instruction manual or contact Hanna Instruments directly for detailed guidance suited to your specific needs.
