Calibrating a pH meter correctly is a necessary step when testing the pH of a solution. Inacurate pH readings usually come from poor calibration, storage and cleaning of the pH meter. These quality and safety methods are thus part of the standard operating procedure (SOP) when calibrating pH meters correctly.

The first step of pH Calibration is gathering equipment to be used in the process. These include the pH meter, a pH electrode and at least two different pH buffer solutions, typically pH 4.01 and 7.0 are used. Sometimes an additional buffer solution of pH 10.0 is used. The buffers serve as reference points for the calibration process.

Inspection and cleaning of the electrode is an important next step to remove any residue from previous measurements.

In a three point calibration, the order of calibration is mid-point (neutral pH7.0), low point (acidic pH 4.01) and high point (alkaline pH10.0).

At each point calibration, the electrode is immersed in the buffer solution and the pH meter adjusted to match the buffer’s pH value. At the end, the adjustments are confirmed by checking the pH meter against the buffer solutions value.

The whole process is documented and an easy to read calibration certificate is provided.