Application of Negligible Depletion Solid-Phase Extraction (nd-SPE) for Estimating Bioavailability and Bioaccumulation of Individual Chemicals and Mixtures

Negligible depletion solid phase (micro) extraction (nd-SPE or nd-SPME) is a new analytical tool for measuring freely dissolved concentrations and partition coefficients. This approach can be applied in identifying bioaccumulative compounds in environmental samples. In this paper, a brief description of the procedure, as well as an overview of several published applications, are presented. The approach is illustrated with two examples: (i) the measurement of humic acid partition coefficients, and (ii) the sreening for bioaccumulative compounds in the environment. Introduction: bioconcentration and bioavailability Bioconcentration as well as bioavailability are two important features in risk assessment. The degree of bioconcentration determines the internal concentration in biota and bioavailability remains a crucial topic in exposure modeling because of its influence on accumulation, biodegradation and other processes in the environment (1-7). Also in toxicology, bioavailability is an important aspect of the potency of chemicals (8), because in principle it is only the freely