Figure 4. SPME fiber sorption kinetics for a wide range of PCB congeners expressed as the C_f/C_w ratio (K) versus extraction time. Data were obtained for HOC concentrations of 1 ng/mL in 130 mL flasks for (a) 7-µm; (b) 30-µm; and (c) 100-µm PDMS coating thicknesses.