Application note: Water activity standards

A change in results when testing salt standards indicates some change in the instrumentation that could be impacting the integrity of product test results.

Since water activity testing is critical to ensure the quality and safety of manufactured products, it is common to find water activity instruments in most quality assurance laboratories. As with any laboratory test method, good laboratory practices require routine verification assessments for water activity to make sure the instrumentation is working properly. This can be accomplished by running tests on standards of known value and comparing the test results to the actual values. While this can be difficult for some common quality assurance tests that do not have independent standards, such as moisture content, water activity standards exist in the form of electrolytic (salt) solutions. These water activity salt standards are one of the most important tools available to laboratory personnel to provide them with confidence in their water activity testing results and facilitate troubleshooting.