Polyoxymethylene solid phase extraction as a partitioning method for hydrophobic organic chemicals in sediment and soot

During the past few years, the presence of soot in sediments has received growing interest. Soot is thought to serve as a strong partitioning medium for specific organic contaminants (PAHs). The precise extent of sorption to this material, however, is poorly known because soot/water distribution coefficients for native PAHs have not been determined yet. Measuring these coefficients using existing partitioning methods is problematic due to the nature of soot. Therefore, the objective of this study was to develop a method for the determination of distribution coefficients for organic contaminants in soot/water (but also sediment/water) systems. The method is based on solid phase extraction (SPE) of chemicals onto the plastic polyoxymethylene (POM). Sorption experiments with POM showed monophasic sorption kinetics, linear isotherms covering several orders of magnitude, and a linear relationship between distribution coefficients for POM and the octanol/water distribution coefficient. Therefore, the sorption process can be considered to be true partitioning. Application of POM for the determination of distribution coefficients for soot and sediment (POM-SPE method) resulted in highly reproducible values. The method was validated by comparing values for sediment with results for the same sediment determined using the cosolvent method. This comparison resulted in an almost 1:1 relationship, proving the method's validity.