Hierarchical porous carbon nanosheets derived from ZIF-on-LDH as coating for solid phase microextraction of polychlorinated biphenyl in beverages

Due to persistence, high toxicity, and tendency to bioaccumulate of polychlorinated biphenyls (PCBs), accurate detection of their residual levels in environmental and food samples is particularly important. To address the challenges posed by complex sample matrices and trace analytes, a new hierarchically porous (micro/mesoporous) carbon nanosheet (HPC-NS) material was designed as sorbent. The HPC-NSs were synthesized using cobalt-based ZIF-67 as self-sacrificial template and layered double hydroxide (LDH) as substrate. These HPC-NSs were applied as fiber coating material for solid-phase microextraction (SPME) to extract and enrich trace amounts of PCBs. By combining headspace SPME with GC–MS/MS, a highly sensitive method was developed for the detection of PCBs in green tea and milk. The proposed method demonstrated a wide linear range (0.2–5000 ng·L −1 ) and low detection limits (0.02–0.06 ng·L −1 ). Experimental results indicated that the HPC-NSs exhibit excellent extraction efficiency toward PCBs, which can be attributed to multiple mechanisms including pore filling, π–π stacking, cation–π interactions, and polar interactions. This work not presents a promising SPME coating material but also offers a robust and sensitive analytical method for detecting trace PCBs in complex matrices.