Conjugated Microporous Polymers with Built-In Magnetic Nanoparticles for Excellent Enrichment of Trace Hydroxylated Polycyclic Aromatic Hydrocarbons in Human Urine

Conjugated microporous polymers (CMPs), linked by a covalent bond to form an extension of the aromatic ring skeleton, are microporous materials characterized by a highly conjugated structure and high stability. The present study reported on a novel strategy for the synthesis of CMPs with built-in magnetic nanoparticles for excellent enrichment of trace hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) in human urine. We modified Fe3O4 nanoparticles with boronic acid groups and then reacted the nanoparticles with reactive monomers of polyphenylene conjugated microporous polymer (PP-CMP) to anchor the magnetic components in the PP-CMP framework. Chemical bonding between Fe3O4 nanoparticles and PP-CMP networks, together with equally firm covalent linkage and rigidity of the PP-CMP network, endows the magnetic PP-CMP with remarkable chemical stability and durability, even in harsh conditions. Magnetic PP-CMP has the characteristics of high conjugation ability, highly porous structure, and magnetism, which makes it an ideal magnetic adsorbent for trace analytes with aromatic conjugation structure. The adsorption mechanism of OH-PAHs on magnetic PP-CMP was investigated and demonstrated that hydrophobic interaction was important for the contribution of interaction between adsorbents and target analytes, together with the assistance of pi-pi stacking interaction. For the application, the magnetic PP-CMP was used for the enrichment of trace OH-PAHs in human urine of both smokers and nonsmokers in combination with high-performance liquid chromatography with fluorescence detection (HPLC-FLD). It showed good selectivity and excellent sensitivity to these OH-PAHs. Their detection limits were low and in the range of 0.01-0.08 mu g.L-1. The OH-PAHs were detected with different amounts from 0.054 to 0.802 mu g.L-1 in urine samples from smokers and nonsmokers. The recoveries were found to be 76.0%-107.8%. The results indicate that the magnetic PP-CMP offers an efficient enrichment method for trace OH-PAHs in human urine.