Solid-phase microextraction for determining the binding state of organic pollutants in contaminated water rich in humic organic matter

Solid-phase microextraction (SPME) in both conventional and headspace mode was used for determining the freely available and reversibly bound fraction of phenols and polycyclic aromatic hydrocarbons in contaminated water rich in dissolved polymeric organic matter (DOM). The SPME results obtained by using internal calibration with deuterated surrogates gave the total analyte concentration based on the identical partitioning behaviour of both, native pollutants and deuterated spikes, and agreed well with data from exhaustive LLE. Data obtained with direct and headspace SPME are very similar. Investigated matrices include both contaminated water and artificial DOM solutions. The DOM compounds were isolated from different aquatic and terrestrial sources and cover a wide range of hydrophobicity. A new approach based on progressive dilution of samples rich in DOM was developed for determining both the freely-dissolved fraction of an unknown analyte and its partition coefficients. Theoretical considerations provide strong evidence that the commonly used term 'concentration' in SPME analysis should be replaced by the more appropriate term 'activity' of the solute. (C) 1998 Elsevier Science B.V. All rights reserved.