pH buffer solutions

pH buffer

The accuracy of your measurement is in direct relation to the accuracy of the pH buffer solution you use to calibrate your pH tester.

A pH measurement is no better than the buffers used for calibration.

What is a pH buffer?

Buffers are aqueous solutions with well defined pH values. A buffer solution contains chemicals that will maintain a constant pH regardless of additions of small quantities of acids or bases i.e. it must have a buffering capacity. This is where the term buffer originates from.

Different types of buffers

Buffers can be classified in three categories. The main difference between the different types of buffers is the accuracy.


Technical buffers

Commercial buffers, or so-called technical buffers, are solutions for practical use and the type of buffers you use for regular pH measurements.

Typical accuracy for a technical buffer is ±0.05 pH units.


Standard buffers

Standard buffer solutions, also called secondary reference buffers, are buffers used as standards for precision measurements and in the manufacture of technical buffer solutions. To be called a standard buffer the buffer has to be produced according to a formula provided by a national standards laboratory, as for example the National Institute of Standards and Technology (NIST) in USA.

Standard buffer solutions have accuracies better than ±0.005 pH units between 0°C and 60°C (32°F and 140°F).

Standard buffers are more susceptible to accidental contamination and dilution than technical buffers. A technical buffer has a higher buffer capacity and is a more robust calibration solution compared to a standard buffer.


Primary reference buffer

Primary reference buffers show the lowest uncertainty in pH values, ±0.003. However, they are not available commercially and are used mainly in metrological institutes.

Traceability

To be able to talk about the accuracy of your pH measurement or your pH calibration solution, you need to understand the concept of traceability.

More

Read more on what to consider regarding pH calibration solutions.

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Download the new release ISO 14001:2015