Sample Preparation for a pH measurement
When preparing the sample for measurement, one needs to take certain rules into consideration.It is very important to either measure the temperature of the sample or keep the temperature constant at a known value. The reason for doing this is that the pH value of a sample is temperature dependent and the pH meter electrode gives a temperature dependent measurement result. This temperature dependence does not pose a problem as long as the temperature is recorded and compensated for.
- Always stir the sample to ensure that it is homogeneous. This ensures that the measured value is valid for the whole sample and not just for the part where the electrode is situated.
- There needs to be enough sample volume in the vessel so that the junctionin the reference part is completely submerged in the sample. This is necessary to ensure that there is contact between the inner and outer part of the reference electrode and that the electrolyte can flow out into the sample.
- It goes without saying that the basic rules of good laboratory practice such as only using suitable, clean and labeled glassware for the samples are also applicable for pH measurements.
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Source of article: A Guide to pH measurement by Mettler Toledo
