Determination of freely dissolved polycyclic aromatic hydrocarbons in human serum using core-shell Fe 3 O 4 @polyacrylate magnetic microspheres by exclusive volume effect.

Freely dissolved concentration is an important parameter for evaluating the bioavailability of compounds. Negligible-depletion solid-phase microextraction (nd-SPME) has been widely used for the determination of freely dissolved compounds but suffered from long equilibrium time. Multifunctional mesoporous composite microspheres have large specific surface area and therefore extraction equilibrium could be reached in a short time. In this study, a novel method was developed for quick determination of freely dissolved polycyclic aromatic hydrocarbons (PAHs) in human serum using core-shell polyacrylate-ferriferous oxide magnetic microspheres (Fe ₃ O ₄ @PA). Mass transfer of PAHs from sample solution to Fe ₃ O ₄ @PA was greatly increased owing to unique properties including large surface area (58.5 m ² g ^-1 ), high pore volume (0.10 cm ³ g ^-1 ) and thin coating layer (50 nm). Freely dissolved PAHs can be selectively extracted because of the mesoporous structure of PA coating layer with uniform pore size of 7.08 nm. However, bound forms of PAHs would not be able to access into pore channels due to size exclusion. In comparison with long equilibration time (139 h) by nd-SPME, equilibrium can be reached within 29 min (t _90% ) using Fe ₃ O ₄ @PA as novel sorbents. The sorption coefficients (log K _BSA ) of PAHs to bull serum albumin (BSA) ranged from 3.36 to 4.87, which are consistent with the values measured by nd-SPME (log K _BSA = 3.64-5.12). Finally, the freely dissolved PAHs (C _free ) measured by the proposed method (0.69-1.92 μg L ^-1 ) have a good agreement with that by nd-SPME (0.56-2.11 μg L ^-1 ), indicating that it is feasible for rapid determination of free forms of compounds in real samples by Fe ₃ O ₄ @PA.
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