Carbonized MOF-coated carbon fibers for an online in-tube SPME-HPLC-DAD method to determine polycyclic aromatic hydrocarbons in water.

To improve the extraction performance of carbon fibers (CFs) to polycyclic aromatic hydrocarbons (PAHs), the carbonized MOF-coated CFs (CFs@C-MOF) were fabricated for online in-tube solid-phase microextraction (SPME). ZIF-8 was grown on CFs at room temperature and subsequently carbonized at 350°C under nitrogen atmosphere. The morphology and composition of the materials were characterized by SEM, BET, XRD, and Raman spectroscopy. The CFs, CFs@MOF, and CFs@C-MOF were separately filled into each tube and evaluated using PAHs as model analytes. The CFs@C-MOF tube demonstrated superior extraction efficiency, with enrichment factors ranging from 414 to 1662. High enrichment effect was attributed to the combined contribution of enhanced hydrophobicity, stronger π-π interactions, and a larger surface area. Following optimization of key parameters (50 mL of sample, 2.0 mL min-¹ of sampling rate, 2.5 % (v/v) of methanol concentration, 3.0 min of desorption), an online in‑tube SPME‑HPLC‑DAD method was established. The method achieved a detection limit of 0.01 μg L-¹, with linear ranges of 0.05-10.0 μg L-¹ for acenaphthylene and 0.05-5.0 μg L-¹ for the other seven PAHs. The method was successfully applied to determine trace PAHs in water samples and exhibited advantages in sensitivity, repeatability, and online operation, providing a viable strategy for detecting other organic pollutants.