Calibration & Care of pH Meters
The most recent newsletter from Water Online had a link for cleaning, inspecting, and calibrating pH meters. We aren't advocating for Water Online, or any trade group out there, but we subscribe to dozens of newsletters from a variety of groups like Water Online so that we can give you the best and most up to date info out there. When I tried to look at the information they provided, it required me to register to see the article.
I didn't want to post something here that would require anyone to register, but I really liked the idea of providing you with something practical about pH meters that are part of many of your daily routines. Because our goal is to always provide info that is free and publically available, I did a little searching on the web to see what was out there.
I found that there is a lot of free, publicly available information on calibrating pH meters, as well as on care, storage, and many other topics. One of the best for basic information was all-about-ph.com.
* Good overview of care and calibration from MBH Engineering systems
* Calibration video from NCBioNetwork.org for a Fisher Scientific meter
* Video from Kirkwood Community College
Many of the sites that I found suggested a two point calibration and others, like the videos above, say to use a three point calibration. I'm no expert, so if you aren't sure, ask a technical assistance provider you trust, but if your samples are usually below pH=7, then you should use buffers of pH 7 and 4. If above 7, then use 7 and 10 for the best accuracy.