What buffers should be used to calibrate a pH probe?

Document ID

Document ID TE483

Published Date

Published Date 04/03/2019
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Question
What buffers should be used to calibrate a pH probe?
Summary
Buffers for calibrating a pH probe
Answer
A minimum of two buffers should be used for calibration of a pH meter or tester. If the expected pH of the sample is below 7, use pH 4 and 7 buffers. If the expected pH is above 7, use pH 7 and 10 buffers.  Three pH buffers should be used for samples that are unknown or have differing pH.  pH buffers come in either powder pillows or as solutions.

-Powder pillows have a longer shelf life and are more economical than solutions but are less convenient.  Buffer powder pillows require preparation by mixing with 50-mL deionized water before each calibration.

-Buffer solutions are very convenient but can be prone to contamination if left open. Buffer solutions can be poured from the bottle into a small beaker, or if using Singlet Solution Packs, the electrode can be placed directly in the solution bag.

Once used for calibration, buffer solutions should be discarded. Buffer solutions in bottles should always be poured into a beaker for calibration, and used buffer should never be poured back into the bottle.

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