Estimation of effective diffusion coefficients for benzene and toluene in PDMS for direct solid phase microextraction

Polydimethylsiloixane (PDMS) is commonly used as the coated polymer in the solid phase microextraction (SPME) technique. Based on the principle of partitioning, PDMS/SPME can be a fast, economic and solvent-free sampling method to extract volatile organic compounds (VOCs) from gaseous or aqueous samples. This study experimentally investigated the adsorption of benzene and toluene onto PDMS/SPME, and estimated the effective diffusion coefficients of benzene and toluene in the PDMS coating. The results showed that the effective diffusion coefficients of these two compounds did not change with the concentrations of the gaseous or aqueous samples. The effective diffusion coefficients were found to linearly increase with the stirring speeds of the aqueous solution. The empirical model proposed in this study can be used to estimate the effective diffusion coefficients and extraction time at different stirring speeds, which will contribute to the practical applications of the SPME technique.