Polycyclic aromatic hydrocarbons (PAHs) are concerned due to their carcinogenic and teratogenetic effects to human beings. As an important carrier in blood, serum albumin is able to bind to many chemicals and transports them to all parts of the organism. Therefore, it is crucial to determine the partitioning of PAHs to biological phases to evaluate the bioaccumulation of PAHs in organisms. Due to the aqueous solubility of serum albumin, it is difficult to separate the freely dissolved PAHs from the serum albumin associated PAHs with traditional extraction techniques. Although negligible depletion solid-phase microextraction (nd-SPME) is efficient in sensing the freely dissolved PAHs, it suffers from long equilibration time. In this work, we developed a quick approach for the determination of sorption coefficients of PAHs to bovine serum albumin (BSA) by using Fe₃O₄@nSiO₂@mSiO₂ magnetic mesoporous microspheres. In the synthesis of Fe₃O₄@nSiO₂@mSiO₂ materials, trace amount of hexadecyl trimethyl ammonium (CTAM⁺) template was kept in the mesopores of these materials to function as sorbent for the extraction of PAHs. The mesoporous structure hinders the extraction of BSA associated PAHs due to the volume exclusion effect, and only the freely dissolved PAHs can access into mesoporous and are extracted by CTAM⁺. The large surface area (186 m²/g) and high pore volume (0.16 cm³/g) of the Fe₃O₄@nSiO₂@mSiO₂ microspheres provide enlarged contact area for extraction. Furthermore, the thin mesoporous layer (≈50 nm) shortened the diffusion distance of PAHs from aqueous phase to CTAM⁺ sorbent. These above characteristics enhanced the extraction efficiency and reduced the equilibration time (t_90%) to 66 min, which is less than 1/200 of that by nd-SPME. In addition, the magnetic microspheres can be conveniently collected from the solution after extraction by applying an appropriate magnetic field. Combining the proposed extraction procedure with GC-MS determination, the partition coefficients of PAHs to BSA were measured with values in the range of 10^3.94 to 10^5.00, which were basically consistent with that by nd-SPME (10^3.53～10^4.99).

Key words: magnetic mesoporous microspheres, freely dissolved concentration, polycyclic aromatic hydrocarbons, bovine serum albumin, sorption coefficients