Polydopamine-based immobilization of zeolitic imidazolate framework-8 for in-tube solid-phase microextraction

• A novel and versatile strategy to immobilize MOFs onto PEEK tube.
• ZIF-8-PDA-PEEK showed excellent stability for in-tube SPME.
• ZIF-8-PDA-PEEK showed high extraction efficiency with enrichment factor of 550–734.
• Online SPME–HPLC with LODs of 0.5–5 pg/mL for PAHs.

Zeolitic imidazolate frameworks (ZIFs), a subfamily of metal-organic frameworks (MOFs), have received considerable attention as a novel porous material for sample preparation due to their fascinating structures and unique properties. Here, we developed a novel bio-inspired polydopamine (PDA) method to immobilize ZIFs inside the chemical resistance poly(ether ether ketone) (PEEK) tube for online solid-phase microextraction (SPME). Firstly, PDA layer was assembled inside the PEEK tube. Secondly, attributing to its noncovalent adsorption and covalent reaction ability, PDA could attract and anchor ZIF-8 nutrients onto the inner surface of PEEK tube to promote the nucleation and growth of ZIF-8. The morphology and surface properties of the prepared ZIF-8-PDA-PEEK tube were characterized by scanning electron microscopy and energy dispersive X-ray spectrometry. The ZIF-8-PDA-PEEK tube exhibits excellent extraction efficiency toward six polycyclic aromatic hydrocarbons (PAHs), with enrichment factor from 550 to 734. The developed online SPME–HPLC method shows good linearity (10–5000 pg/mL) and low detection limits (0.5–5 pg/mL) for six PAHs. It also has been used to determine PAHs in environmental samples, with recoveries in the range of 82.5–98.6%.