How do I calibrate my pH electrode?

While there are different types of pH electrodes, and many types of meters, the general calibration steps remain the same.

This is a VERY GENERAL outline of how to calibrate a pH electrode. Always reference the manual for procedures specific to your electrode and meter.

  1. Check that your electrode has been stored properly and that the pH bulb and junction are hydrated.
    1. Has the electrode been stored in HI70300L storage solution? If the electrode is dry, have it rehydrate for at least 1 hr in storage solution before attempting to calibrate it.
  1. Remove your electrode from the storage solution and rinse the electrode with deionized  (DI) water.
    1. Rinsing the electrode with deionized water removes any salts, deposits, or impurities that may be clinging to the electrode glass.
    2. Don't have DI water? RO, distilled, pure, or demi water will work in a pinch!
  2. Use fresh buffers for your calibration.
    1. Select fresh buffers that bracket your calibration range. For example, if your sample is typically around pH 8.0, you will want to calibrate to at least 2 points ie. pH 7.01 and 10.01.
  3. If your electrode is refillable, open the fill cap.
  4. Ensure that the electrolyte level is at least 1 cm below the fill hole. If not, top-off the internal electrolyte.
  5. Pour your buffers into a clean beakers and put a stir bar into the beaker, and set it stirring on a magnetic stirrer.
    1. If you are using a sachet, you can swirl the electrode carefully around in the sachet.
  6. Turn on your meter and access calibration mode.
  7. Submerge the electrode in the buffer, and make sure the junction is covered.
  8. Allow the reading to stabilize. Some meters will automatically accept the calibration when the reading is stable, others you have to press a button to accept it.
  9. Once that buffer is accepted, remove the electrode from the buffer.
  10. Rinse the electrode with DI water before moving onto the next buffer.
  11. Repeat the rinsing, submerging, waiting to stabilize, and rinsing, until you have calibrated to all of the calibration points you need.
  12. Ensure the calibration is saved, and exit calibration mode.
  13. Rinse the electrode one more time.
  14. You're ready to test!

Some videos that demonstrate calibration procedures are: