Simple Tips to improve reliability of pH measurements

Measuring pH of a solution

pH plays a crucial role over control of course of chemical and biochemical reactions and therefore finds widespread use in laboratories and manufacturing industries. Slightest variations in pH can result in erroneous results of reactions or yields in manufacturing operations.

A pH meter is a delicate device and should be handled with care. Additionally, some tips are being offered in the present article to ensure high reliance on your pH measurements.

Measuring pH of a solution
Measuring pH of a solution

Condition the new electrode

New electrodes are shipped with rubber caps affixed to the sensor bulbs or tips to keep the sensor moist with 4M KCl solution. Remove the end cap and rinse the sensor with deionized water. Subsequently, soak in 4 M KCl for about half an hour and rinse with deionized or distilled water. Conditioning in water is not recommended as it can damage the glass membrane of the sensor.

Keep sensor hydrated at all times

The sensor should not be allowed to dry out. A dry bulb will not give correct results. Always keep the bulb immersed in a beaker filled with 4M KCl in between readings. In case long time storage is required then cover the sensor bulb with the rubber cap filled with 4M KCl

 Maintain Electrolyte level inside junction cell

Regularly inspect the level of electrolyte inside the electrode to make sure that the reference wire remains immersed. Dried out junction will result in increased errors accompanied with solid salt deposition at the junction. However, while filling make sure that the level is below the filling hole.

Remove or loosen electrolyte fill cap during use

Loosening or removal of the cap allows sufficient air to enter and improve the stability of readings.

 Carry out daily calibration

It is mandatory to calibrate the pH meter before use. Rinse the electrode with purified water before immersion in any solution. After rinsing do not wipe the bulb as this will disturb the glass membrane. Instead gently soak the water droplets with a tissue paper. A single point calibration can be carried out but a three-point calibration covering standard pH buffers at 4.0,7.0 and 9.0 is recommended to cover the entire pH range generally encountered.

Ensure probe is always clean

Always keep pH probe clean. Unclean probes result in drifts or erratic results. Soak the electrode in a cleaning solution available commercially for about 15-20 minutes. Rinse in water and carefully soak any sticking droplets using tissue paper. Avoid rubbing as it can damage the glass membrane. An unclean probe will contaminate the solution or buffer into which it is immersed.

 Maintain temperature during observations

 pH measurements are temperature dependent. Make sure that the temperature does not fluctuate during the observations.

 Follow recommended storage conditions

As recommended the sensor should be immersed in 4.0M KCl or pH 4.0 standard buffer when it is sitting idle. For long-term storage insert the electrolyte filled cap over the sensor bulb. Never store bulbs immersed in water as this can result in changes in electrolyte concentration inside the sensor either by leaching to outside water or by transfer of water from outside.

The tips outlined above are simple to observe and will help in getting reliable and accurate data every time you record pH measurements.

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  1. Thanks Doctor for the fantastic lecture on ph measurements.


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