Why are 4 pH and 7 pH buffers recommended over a 10 pH buffer for calibration?
pH sensor calibration
A 10 pH buffer solution is unstable because it absorbs carbon dioxide (CO2) from the air. When CO2 is absorbed in water, it forms carbonic acid, which lowers the pH of the buffer. To prevent potential problems from calibrating with inaccurate pH 10 buffer solutions, we recommend calibrating with 4 pH and 7 pH buffers. This establishes a slope value which carries over to the high pH side. A 10 pH buffer can be used but we recommend using fresh 10 pH buffer whenever possible.