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Illustration of calipers and ph colors for article on pH meter calibartion.
Published On: August 16th, 2022

The calibration of the pH meter using an SOP (standard operating procedure/protocol) is highly important and serves a very important purpose – keeping the data that the electrodes generate within specifications. pH determinations need several measurement, calibration, and maintenance processes. If an electrode is not properly calibrated, it can lead to inaccurate readings. These small components play a large part in safety and quality and must work properly.

To keep electrodes in top shape, standard operating protocols, such as calibration of the pH meter using SOP, are put in place to ensure efficient operation.


Materials You’ll Need

You’ll need certain materials before you begin calibration of the pH meter using SOP. Items to have in your laboratory include:

  • pH calibration buffers (pH 4.01, 7.01, 10.01, etc.)
  • Beakers
  • pH electrode storage solution
  • pH electrode clearing solution 
  • pH meter with electrode 
  • Pure water (such as deionized, reverse osmosis, and distilled)


Calibration of the pH Meter with SOP: Setting Up for Measuring

pH meter calibration is essential. The end goal is measurement and maintenance, and calibration of the pH meter with SOP is an integral part of reaching that goal.

Before calibrating, you’ll have to set up for calibration and measurement, including electrode preparation. As you prepare the electrode, there are several steps to follow so that calibration of the pH meter with SOP can occur. Steps include:

  • Removing the electrode’s cap
  • Looking for any scratches or breaks within the electrode
  • If the electrode has breaks or cracks, use a new electrode
  • Shaking the electrode downward to ensure there are no glass bubbles in the bulb
  • Checking to make sure the electrode was stored and cleaned properly (this is part of SOP maintenance)
  • Rinsing off the electrode with pure water, which removes salt deposits

Once this process is complete, you’re ready to begin calibrating the pH meter with SOP.


The Process of Calibration of the pH Meter with SOP

Such as with setting up, there is a particular process for calibration. So, how to calibrate a pH meter? The precise steps include:

  • Filling a beaker with pH calibration buffer to cover the electrode junction (usually ¾ full of a 100mL beaker)
  • Placing the electrode inside of the beaker and stirring gently with the pH calibration buffer 
  • Confirming the calibration point:
    • When the reading is stable
    • When digits don’t change for five seconds
  • Repeating for other calibration points
  • Rinsing with pure water between calibration points and drying the probe

The buffers only have a certain lifetime, so calibration must be performed when necessary. In general, pH 4 and pH 7 buffers last four to eight weeks, and alkaline pH buffers last one to two weeks.


What Happens After Calibration?

After the pH meter’s calibration using SOP, more processes must be performed with the electrode. Next, you’ll be measuring for liquid samples, repeating SOP after each sample, and measuring solid samples. Instead of pure water, measuring solid samples involves a knife or auger to make a hole for the pH electrodes.

After measurement, proper maintenance and storage of the electrodes are paramount, Like other processes, SOP should be utilized here.

Hudson Robotics has been the leading supplier of automated products for over 38 years. To learn more about pH meter calibration using SOP, speak to a representative today!