A pH meter or pH meter is a scientific instrument that measures the activity of the hydrogen ion in aqueous solutions, indicating its degree of acidity or alkalinity expressed as pH. The pH meter measures the difference in electrical potential between a pH electrode and a reference electrode. This difference in electrical potential is related to the acidity or pH of the solution. The pH meter is used in many applications ranging from laboratory experimentation to quality control.
There are general maintenance techniques for pH meters, but in many cases each brand and each model has its own care. We will have to follow the instructions of the meter manufacturer to be able to enjoy it for a longer time.
If in addition to the corresponding calibrations, we perform an adequate maintenance of the meter electrode, we will ensure a longer life and more accurate results in each measurement. Many pH meters incorporate glass sensors and reference tubes that must be stored in specially formulated solutions. If a handheld meter is used, the storage solution is usually found on the meter cover. Do not spill the solution in which the sensor is located, as we will need it. For most pH sensors, it is essential that the sensor is stored wet in the appropriate solution.
To clean the pH meters, you can use cleaning solutions, then replace the sensor in your storage solution. Most pH electrodes have a shelf life of approximately 1-2 years. If you are experiencing an irregular reading and have difficulty calibrating, it may be time to replace the electrode (or the meter, if it does not have a replaceable electrode).
Calibration and Maintenance
Very precise measurements require that the pH meter be calibrated before each measurement. More typically, calibration is performed once a day of operation. Calibration is necessary because the glass electrode does not provide reproducible electrostatic potentials during periods of extended use times.
The calibration is carried out with at least two standard buffer solutions that cover the range of pH values to be measured. For general purposes, buffers at pH 4.00 and pH 10.00 are suitable. The pH meter has a calibration control to set the meter reading equal to the value of the first standard buffer and a second control that is used to adjust the meter reading to the value of the second buffer. A third control allows to adjust the temperature. More precise measurements sometimes require calibration at three different pH values.
Good laboratory practices dictate that after each measurement the probes are rinsed with distilled water to eliminate any trace of the solution that is measured, cleaned to absorb the remaining water that could dilute the sample and alter the reading.
Some tips and tricks
- Always read the instruction manual before use. We must not forget that although the instructions can be boring, they will generally answer the questions we have about the correct use and care of the pH meter, thus achieving a more lasting and fruitful life for ours.
- Always make sure that the pH meter has been calibrated correctly.
- If the handheld meter includes a storage solution in the lid, store the meter in a vertical position for the most efficient saturation.
- Never touch a sensor electrode or reference cell with your fingers: the skin oil affects the readings and may permanently damage the pH sensor. Clean the electrode with the cleaning solutions created for this purpose.
- Always move the pH meter in the water or solution to eliminate air bubbles.
- Store the pH meter in a cool, dry place.
- Do not store it in distilled water.
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