Water Activity Standards are ready-to-use reference solutions designed for routine water activity meter calibration, verification and quality-control checks.
Each individual reference level is supplied as a box of 50 single-use vials, helping laboratories avoid the preparation errors, contamination and variability that can occur when salt solutions are mixed manually.
Reference values are available from 0.250 to 1.000 aw, allowing food manufacturers, QA/QC laboratories, pharmaceutical facilities, research laboratories and other water-activity users to select standards that bracket the normal operating range of their products.
Each standard is supplied with a Certificate of Analysis providing lot-specific reference information for documentation and instrument-performance checks.
| Cambridge SKU | Reference Value | Solution Type | Format |
| WAS-250 | 0.250 aw | Lithium chloride (LiCl) | 50 single-use vials |
| WAS-350 | 0.350 aw | Lithium chloride (LiCl) | 50 single-use vials |
| WAS-500 | 0.500 aw | Lithium chloride (LiCl) | 50 single-use vials |
| WAS-760 | 0.760 aw | Sodium chloride (NaCl) | 50 single-use vials |
| WAS-920 | 0.920 aw | Sodium chloride (NaCl) | 50 single-use vials |
| WAS-984 | 0.984 aw | Potassium chloride (KCl) | 50 single-use vials |
| WAS-1000 | 1.000 aw | Water | 50 single-use vials |
| WAS-KIT | Assorted | Multiple reference solutions | Assorted kit |
A water activity standard is a solution with a known equilibrium water activity value that can be measured by a water activity meter to check whether the instrument is reading correctly.
Rather than assuming a meter remains accurate indefinitely, laboratories can periodically measure a known standard and compare the displayed result with the certified or specified reference value.
Depending on the instrument and manufacturer's procedure, the result may be used for:
Measuring a known standard verifies how the instrument is performing. Some water activity meters then allow the operator to adjust or calibrate the instrument if the result falls outside the manufacturer's acceptable tolerance. Always follow the calibration and verification procedure specified for your particular meter.
For routine QA/QC, it is generally more useful to select reference standards near or on either side of the normal water activity range of your products rather than relying on a reference point far outside your working range.
For example:
| Typical Product aw Range | Useful Standards to Consider |
| Approximately 0.25–0.50 aw | 0.250 and 0.500 aw |
| Approximately 0.50–0.76 aw | 0.500 and 0.760 aw |
| Approximately 0.76–0.92 aw | 0.760 and 0.920 aw |
| Approximately 0.92–0.98 aw | 0.920 and 0.984 aw |
Your instrument manufacturer may recommend specific standards, verification frequencies or calibration points. Follow those instructions when they differ from a general bracketing approach.
Using two reference points can provide more information about instrument performance than checking only one value.
One standard can confirm the meter at a particular point, while two appropriately selected standards can help determine whether instrument response remains reasonable across the range where your products are normally measured.
Some manufacturers specifically recommend selecting standards above and below the expected sample range.
If most of your products measure around 0.65–0.75 aw, the 0.500 and 0.760 aw standards may provide more useful verification points than checking only against 1.000 aw. Always confirm the appropriate procedure for your specific meter.
Preparing water activity standards manually requires accurate reagent concentration, weighing and solution preparation.
Pre-made single-use reference solutions eliminate much of this preparation work.
Benefits include:
Once a reference vial is opened, evaporation, contamination or transfer of material can change the composition of the solution.
For this reason, a fresh vial should be used according to the manufacturer's instructions rather than pouring a used standard back into its original container or repeatedly reusing an opened reference solution.
Use enough solution to properly cover the bottom of the sample cup according to your meter's operating instructions and discard the used solution after the verification or calibration procedure.
Water activity is temperature dependent.
Reference standards and the meter should be allowed to reach stable and comparable temperature conditions before making decisions about instrument performance.
For consistent results:
Every water activity meter has a published measurement accuracy. A displayed result does not need to exactly equal every decimal place printed on the standard in order for the instrument to be operating within specification.
Compare the difference with the meter's stated accuracy, the standard's Certificate of Analysis and the manufacturer's verification criteria before adjusting the instrument or assuming that either the meter or standard is defective.
A common question is whether a water activity meter is faulty when a 0.760 aw standard displays 0.77 aw.
The difference is only 0.010 aw.
Whether this result is acceptable depends on the published accuracy and verification requirements of the particular meter being used.
For example, an instrument with a stated accuracy of ±0.02 aw would not automatically be considered faulty solely because it displayed 0.77 aw against a nominal 0.760 aw reference.
If a result appears questionable, allow the meter and standard to reach stable temperature conditions and repeat the test with a fresh vial before making an adjustment.
Supplied Certificate of Analysis for its water activity standards.
The certificate identifies information such as:
Documentation states that measurement equipment used during preparation and testing is calibrated to approved national and international standards.
Keep the lot-specific Certificate of Analysis with your laboratory or QA/QC records when traceability documentation is required.
Shelf life is lot specific and should be confirmed from the package and Certificate of Analysis.
Documentation for current standards indicates validity based on the date of manufacture when the package remains intact and is stored under normal laboratory conditions.
Do not use expired, leaking, damaged or previously opened reference vials for formal instrument verification.
Water activity standards are particularly important in food-production laboratories where aw results may be used for:
Routine verification helps provide confidence that a water activity meter is performing as expected before product decisions are based on its results.
Shelf-life studies often involve comparing relatively small differences between samples over time.
Checking instrument performance with a known reference standard before or during a study can help distinguish actual product changes from potential instrument drift.
Water activity remains only one part of shelf-life assessment and should be evaluated alongside appropriate microbiological, chemical, sensory, packaging and storage information.
Water activity testing can also be used in pharmaceutical, natural health product and cosmetic development or QA/QC when aw is relevant to the product specification or test method.
Examples may include:
Regulated laboratories should confirm that the reference standard, calibration procedure, documentation and instrument performance meet the requirements of their applicable method or quality system.
These solutions provide known water activity reference values, but the calibration or verification procedure is determined by the instrument manufacturer.
Before using a third-party standard to adjust an instrument, confirm:
Cambridge can help review the appropriate standard values for the water activity meter you are using.
Cambridge supplies several PCE water activity meters, including:
Different PCE models have different accuracy specifications and calibration capabilities. Follow the instructions for the exact model rather than applying one calibration procedure to the entire product family.
| Standard | Reference Level | Typical Reason to Select |
| WAS-250 | 0.250 aw | Low-aw products, dried powders and lower-range instrument checks |
| WAS-350 | 0.350 aw | Additional low-range reference point for dry products and formulation work |
| WAS-500 | 0.500 aw | Common mid-low reference for dry foods, powders and ingredients |
| WAS-760 | 0.760 aw | Useful mid-range reference for many intermediate-moisture food applications |
| WAS-920 | 0.920 aw | Higher-aw products and upper-range verification |
| WAS-984 | 0.984 aw | Near-upper-range instrument checks |
| WAS-1000 | 1.000 aw | Upper endpoint / water reference where appropriate to the instrument procedure |
| WAS-KIT | Assorted | Laboratories requiring multiple aw reference points |
Water activity standards provide known aw reference values that can be used to verify the performance of a water activity meter and, where permitted by the meter manufacturer, perform calibration or adjustment.
Individual water activity standards are supplied in boxes of 50 single-use vials.
Cambridge offers reference values of 0.250, 0.350, 0.500, 0.760, 0.920, 0.984 and 1.000 aw, plus an assorted standards kit.
Yes. upplied lot-specific Certificate of Analysis documentation with its water activity standards.
They are intended as single-use reference solutions. Once opened and exposed to the environment, the solution can be affected by evaporation or contamination and should not be relied upon for repeated formal verification.
This depends on the meter manufacturer's procedure and your quality system. Two standards around the normal measurement range can provide a more useful check of instrument response than a single reference point.
Choose standards appropriate to the aw range you normally measure and follow the recommendations for your instrument. A laboratory testing near 0.70 aw, for example, may consider standards such as 0.500 and 0.760 aw.
Water activity meters and reference standards both have defined tolerances, and temperature also affects water activity. Compare the result with the meter's accuracy specification, the standard's Certificate of Analysis and the manufacturer's verification tolerance rather than expecting every displayed digit to match exactly.
Not necessarily. The difference between 0.760 and 0.770 aw is 0.010 aw. Whether that result is acceptable depends on your meter's stated accuracy and verification procedure. Repeat the check under stable temperature conditions with a fresh vial before concluding that the meter or standard is defective.
Yes. Water activity is temperature dependent. Allow the meter and reference solution to reach stable and comparable conditions and follow the temperature information supplied with the standard.
These solutions provide known aw reference values, but calibration and verification procedures vary between PCE models. Confirm that the selected reference point and procedure are supported by your exact PCE meter before making an adjustment.
The VEE GEE 47002 supports water activity calibration using reference standards. Follow VEE GEE's instructions for the selected measurement mode and reference points.
Yes. Check the expiration date on the package and lot-specific Certificate of Analysis. Do not use expired or damaged standards for formal instrument verification.
No. These are prepared single-use reference solutions supplied in individual vials. Reusable saturated salt standards use a different format and handling procedure.
Cambridge Environmental Products supplies water activity calibration and verification standards in Canada from 0.250 to 1.000 aw, along with water activity meters, sample cups and related QA/QC equipment.
Cambridge Environmental Products supplies water activity meters, reference standards, sample cups and related QA/QC equipment across Canada.
If you are unsure which reference standards to order, send us the water activity meter model, normal sample aw range, required verification frequency and any internal QA or calibration requirements.
The most useful standards are normally those that match or bracket the water activity range your laboratory measures most often.
Send Cambridge your meter model and typical product aw range and we can help determine which reference points make the most sense for your verification program.
