Determination of distribution coefficients of priority polycyclic aromatic hydrocarbons using solid-phase microextraction

The determination of distribution coefficients is important for prediction of the chemical pathways of organic compounds in the environment. Solid-phase microextraction (SPME) is a convenient and effective method to measure the distribution of chemicals in a two-phase system. In the present study, the SPME distribution coefficient (K(spme)) of 16 priority aromatic hydrocarbons (PAHs) was determined with 100-microm poly(dimethylsiloxane) (PDMS) and 85-microm polyacrylate (PA) fibers. The partition coefficients and LeBas molar volumes were used to describe the linearity of the log K(spme) values of PAHs. Also, the validation of the distribution coefficient was examined using different sample volumes. The extraction time was dependent on the types of PAHs, and 20 min to 60 h was needed to reach equilibrium. The determined log K(spme) values ranged from 3.02 to 5.69 and from 3.37 to 5.62 for 100-microm PDMS and 85-microm PA fibers, respectively. Higher K(spme) values of low-ring PAHs were observed using 85-microm PA fiber. Good linear relationships between log K(ow) and log K(spme) for PAHs from naphthalene to benzo[alpha]pyrene and from naphthalene to chrysene for 100-microm PDMS and 85-microm PA fibers, respectively, were obtained. The correlation coefficients were 0.969 and 0.967, respectively. The linear relationship between log K(spme) and the LeBas molar volume was only up to benz[alpha]anthracene for 85-microm PA fiber and up to chrysene for 100-microm PDMS fiber. Moreover, the effect of sample volume can be predicted using the partition coefficient theory and excellent agreement was obtained between the experimental and theoretical absorbed amounts of low-ring PAHs. This result shows that the determined log K(spme) is more accurate than the previous method for estimating analytes with log K(ow) < 6 as well as for predicting the partitioning behaviors between SPME fiber and water.