High-throughput screening of bisphenols using magnetic covalent organic frameworks as a SELDI-TOF-MS probe

Core-shell structured magnetic covalent organic framework (Fe₃O₄@COF) nanospheres were rapidly synthesized at room temperature using the monodisperse Fe₃O₄ nanoparticles (NPs) as magnetic core and benzene-1,3,5-tricarbaldehyde (BTA) and 3,3'-dihydroxybenzidine (DHBD) as two building blocks (denoted as Fe₃O₄@BTA-DHBD), respectively. They can serve as a mass spectrometry probe for rapid and high-throughput screening of bisphenols (BPs) from pharmaceuticals and personal care products (PPCPs) by surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF-MS). The Fe₃O₄@BTA-DHBD nanospheres showed some superior features involving average pore size distribution (2.82 nm), high magnetization values (42.5 emu g^-1), high specific surface area (82.96 m² g^-1), and good chemical/thermal stability. It was used as both ideal adsorbent for enrichment of BPs and new substrate to assist ionization in SELDI-TOF-MS. The method exhibited good linearity in the range 0.05-4000 ng mL^-1 with correlation coefficients (r) higher than 0.9920. Low limits of detection (LODs) (500 pg mL^-1 for bisphenol A (BPA), 2 pg mL^-1 for bisphenol B (BPB), 28 pg mL^-1 for bisphenol C (BPC), 60 pg mL^-1 for bisphenol F (BPF), 33 pg mL^-1 for bisphenol AF (BPAF), 200 pg mL^-1 for bisphenol BP (BPBP), 10 pg mL^-1 for bisphenol S (BPS), 90 pg mL^-1 for tetrabromobisphenol A (BPA(Br)₄), and 380 pg mL^-1 for tetrabromobisphenol S (BPS(Br)₄)) and good recoveries (80.6-115%) of BPs in PPCPs were achieved. The relative standard deviations (RSDs) of spot-to-spot (n = 10) and sample-to-sample (n = 5) were in the ranges 5-11% and 5-12%, respectively. The dual-function platform was successfully applied to the quantitative determination of BPs in PPCPs. It not only expanded the scope of the application of COFs but also provided an alternative strategy for the determination of hazardous compounds in PPCPs. Graphical abstract Schematic representation of the synthesis of core-shell structured magnetic covalent organic framework nanospheres (Fe₃O₄@COFs) and its application in the analysis of bisphenols by using Fe₃O₄@BTA-DHBD nanospheres as a MS probe based on surface-enhanced laser desorption/ionization time-of-flight mass spectrometry.