Defective porous urchin-like ZnO/NiO microspheres-coated solid-phase microextraction fiber for analysis of trace polychlorinated biphenyls in milk

Owing to the high lipophilicity of polychlorinated biphenyls (PCB), they easily accumulate in dairy products. Although usually present at very low levels, they pose a serious threat to human health. Therefore, developing a sensitive and reliable method for detecting PCB in dairy products is crucial. Herein, Herein, a metal-organic framework (MOF) material named with bimetallic nodes and double ligands was prepared as a precursor using a one-pot hydrothermal method. Defective porous urchin-like ZnO/NiO, derived from these MOF-based precursors (ZnNi-MOF-NH₂) as a sacrificial template, was synthesized via pyrolysis to remove heat-sensitive ligands. To the best of our knowledge, this urchin-like nanostructured ZnO/NiO hybrid was utilized as a solid-phase microextraction (SPME) coating for the first time. Headspace SPME (HS-SPME) was developed for non-contact extraction of PCB in milk prior to gas chromatography-tandem mass spectrometry (GC-MS/MS) analysis. Under optimal conditions, the HS-SPME-GC-MS/MS method exhibited a wide linear range (0.01-1000 ng·L^-1), low limits of detection (0.003-0.025 ng·L^-1), and high enrichment factors (5714-9906). Additionally, the performance of the ZnO/NiO SPME fiber coating showed no noticeable decrease after 175 uses. The method was applied to trace PCB analysis in milk samples, yielding recoveries of 70.3-114.1 %. The ZnO/NiO derived from MOF-based material provides a promising candidate for SPME coatings to extract PCB and other analogs.