847­-483-9950

Water Accommodated Fraction Analysis (WAF)

When performing a Water Accommodated Fraction analysis prior to sample testing, the material is first equilibrated into the aqueous form and then monitored over time to establish a concentration representative of the sample to use during testing.

When complex substances are only partially soluble in water and are undergoing Toxicology or Biodegradability testing, agencies such as the Organization for Economic Cooperation and Development (OECD) allow certain adaptive pre-analysis methods to address these solubility issues.  This includes preparing water-accommodated fractions (WAFs) of the material.

Water Accommodated Fraction Analysis

The Graph above shows the Water Accommodated Fraction Analysis for a material that intended to undergo biodegradability testing.  The material has extremely low solubility and therefore required a long WAF analysis.

The term “water accommodated fraction” applies to an aqueous media containing only a fraction of multi-component substances that dissolve and/or are present as a stable dispersion or emulsion.

In order to achieve an equilibrated concentration of the dissolved and dispersed components in the aqueous phase, the WAF analysis measures the amounts of substances added directly to water and mixed for a period of time. The material is first equilibrated into the needed solution and then monitored over to time establish a concentration representative of the sample.

WAF analysis is one of the allowed analyses to perform prior to tests where solubility is a key factor.  Hexane, on the other hand, may address solubility issues; however, it is difficult to determine if the carbon contribution is from Hexane residue or the test sample.  As a result, a pre-determination will have to be done before the test, which adds an additional step to confirm that all the hexane has been removed from the test sample. 

For more information on WAF, please contact our Laboratory at 847-483-9950 or info@situtest.com.