A stable isotope dilution method for measuring bioavailability of organic contaminants

Methods for determining bioavailability of organic contaminants suffer various operational limitations. We explored the use of stable isotope labeled references in developing an isotope dilution method (IDM) to measure the exchangeable pool (E) of pyrene and bifenthrin as an approximation of their bioavailability in sediments. The exchange of deuterated bifenthrin or pyrene with its native counterpart was completed within 48 h. The derived E was 38–82% for pyrene and 28–59% for bifenthrin. Regression between E and the sum of rapid and slow desorption fractions obtained from sequential desorption showed a slope close to 1.0. The ability of IDM to predict bioavailability was further shown from a strong relationship (r2 > 0.93) between E and bioaccumulation into Chironomus tentans. Given the abundance of stable isotope labeled references and their relatively easy analysis, the IDM has the potential to become a readily adoptable tool for estimating organic contaminants bioaccessibility in various matrices.

► An isotope dilution method (IDM) was developed to determine HOCs bioavailability.
► The IDM allows the estimation of the exchangeable pool (E) of organic contaminants.
► E values were validated against Tenax desorption and bioaccumulation fractions.
► Stable isotopes were used to make the IDM a low-cost and readily adoptable tool.
► IDM may be incorporated in the risk assessment of HOC-contaminated sediment or soil.