Experts at Ohaus have put together a list of tips on pH calibration. Highlights include the following:

• How often does the pH electrode need to be calibrated?
  • The frequency of electrode calibration is dependent on the precision requirement, sample temperature, surrounding environment and process arrangement of sample test (for example, interference ingredient, flushing and storage, etc.).
  • In order to ensure the accuracy of measurement results, we recommend you calibrate it frequently, preferably one calibration or verification every 10 measurements.
  • If the sample has a complex composition or the electrode is used frequently, you should increase the frequency of calibration.
• What should be done if the pH calibration slope is higher than 105%?
  • Check the buffer solution’s expiry or whether it has been polluted. If it expired, use a new buffer solution.
  • Check whether you have selected the correct buffer solution.
  • The buffer solution group is set wrong. Select the correct buffer solution group as per the buffer solution used.
• Why does the result of pH measurement fluctuate for a long time?
  • Generally, it requires 1-4 minutes for the reading of a pH measurement to be stable. If it exceeds a reasonable time, then see the following:
    • The selected pH electrode cannot handle the present sample.
    • Electrode is aged.

The Ohaus Starter 5000 pH Bench Meter offers everything you need for accurate pH measurement.