Measurement of free concentrations using negligible depletion-solid phase microextraction (nd-SPME)

Measurement of free concentration is necessary to determine the effective or bioavailable quantity of a chemical, and is also a way of determining the binding affinity or partition coefficient of a compound. This review gives a brief overview of the methods available to measure free concentrations and will focus on negligible depletion-solid phase microextraction (nd-SPME). Theoretical as well as experimental details of the method are discussed, including potential confounding factors, such as fouling, diffusion layer effects, and calibration. (C) 2003 Published by Elsevier B.V.