Applications Of Solid-Phase Microextraction In Measuring Partition Coefficients Between Poly(dimethyl)siloxane-Coated Fiber And Water And Freely Dissolved Concentrations Of Hydrophobic Organic Chemicals In Sediment Porewater

This paper focuses on the mechanism for sorption of hydrophobic organic chemicals (HOCs) into poly(dimethyl)siloxane (PDMS) coated solid-phase microextraction and the feasibility for application of SPME in measuring freely dissolved porewater concentrations of VHOCs. The main contents and results are summarized as follows:The first part of the thesis gives a brief overview of the methodology, application and prospects of the SPME technology and emphasizes on negligible depletion-SPME which was employed as a biomimetic tool to determine freely dissolved concentrations of organic chemicals in complex systems.In the second part, a static SPME procedure combined with liquid-liquid extraction was developed to determine the PDMS-water partition coefficients (K_f) of polybrominated biphenyls (PBBs). The accuracy of the measurements of analyte concentrations in the aqueous phase was ensured with a one-to-one recovery correction strategy employing one isomeric PBB congener as a surrogate standard for each PBB counterparts. The results suggested that the time to equilibrium increased with increasing coating thicknesses and there was no significant difference in K_f values among different PDMS coating thicknesses for all six analytes. In addition, a good linear relationship (r² = 0.952) was found between log K_f and log K_ow, but the nonlinear relationship for polychlorinated biphenyls obtained previously could not be adequately verified based upon the present results because the log K_ow values of the target compounds used herein are all less than 7.5.In the last part, a prototype sensor based on SPME was developed and the performance in measuring freely dissolved porewater concentrations of HOCs was evaluated by kinetic experiments which were carried out under laboratory controlled conditions. The preliminary results of the present study demonstrated that the sampler developed herein is a useful tool for determining freely dissolved concentrations of HOCs in complex systems. This device is simple to operate, sensitive, amenable to deployment and suitable for field and on-site application as compared to other techniques.