Water Activity Consumables 4

Water activity standards are used to check the performance and calibration of water activity instruments. These standards have specific known water activity values that cover the entire water activity range. There are two main types of water activity standards, saturated salt slurries, and unsaturated salt solutions. Either standard can be used to verify and calibrate water activity instruments and as would be expected both standard options have advantages and disadvantages.

The advantage of saturated slurry standards is that they can be reused for up to three years, if maintained properly, and are easily prepared without a precision balance and complicated recipes. Their disadvantage is that they take longer to equilibrate and are temperature sensitive.

The advantage of unsaturated salt standards is that they can be made to any water activity value, are faster to equilibrate and are less temperature sensitive. The disadvantage of unsaturated standards is that they are single-use only and must be purchased as a consumable.

The availability of both standards ultimately allows the user to choose the standard type that best fulfills their needs. Novasina is the only water activity provider that provides both types of standards: saturated salt slurry standards called SAL-T and unsaturated salt solution standards called SAL-F.

In addition to using water activity standards, Novasina has specially designed filters to be installed in your water activity meter’s measurement chamber to provide protection against chemical contamination and degradation of the resistive electrolytic sensor element. The inner part of the sensor consists of a liquid, and therefore volatiles which dissolve and dissociate are extremely dangerous and harm the sensor in a very short time frame. For more information on when a filter would be needed, or which is best for your use, click here.

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