Sorption of hydrophobic organic compounds on nonpolar SPME fibers and dissolved humic organic matter - Part III: Application of the solubility parameter concept to interpret sorption on solid phase microextraction (SPME) fiber coatings

Hydrophobic organic compounds (HOCs) sorption on nonpolar poly (dimethylsil oxane) (PDMS) and polar polyacrylate (PA) fiber coatings is based on partit ioning. By applying solubility parameter concept, explaining HOCs' sorption on amorphous polymers including "liquid" SPME coatings, Hildebrand solubil ity parameters (delta) of these fiber coatings can be calculated using fibe r distribution coefficients (K-f) Hildebrand solubility parameters turned o ut to be decisive parameters for describing sorption on both coatings under study. Calculated solubility parameters of PDMS and PA coatings are within a very narrow range delta (PDMS) = 15.0 +/- 1.0 (J(0.5) cm(-1.5)) and delt a (PA) = 22.2 +/- 1.0 (J(0.5) cm(-1.5)) when PAH and PCB fiber distribution coefficients are used to calculate data. Solubility parameter of the 7 mum PDMS coating is slightly, but significantly higher than the 100 mum coatin g. Once calculated, coating solubility parameter may serve to calculate K-f values of hydrophobic analytes based on available physicochemical data inc luding octanol-water coefficients (K-OW) and molar volumes (V-m). Sorption coefficients on nonpolar PDMS and polar PA fiber coatings, available in the literature, fit well in this universal one-parameter solubility concept. F iber distribution coefficients and corresponding octanol-water coefficients follow a strong correlation for analytes of the same "family." For analyte s possessing delta (i) congruent to 21.5 J(0.5) cm(-1.5), relation Log K-f, K-PA = Log K-OW is valid. (C) 2001 John Wiley & Sons, Inc.