Covalent organic framework coating with abundant hydrogen bonding sites for efficient enrichment and sensitive detection of oxygenated polycyclic aromatic hydrocarbons in tea

Monitoring trace oxygenated polycyclic aromatic hydrocarbons (O-PAHs) in tea infusions is crucial, as long-term consumption of O-PAHs-contaminated tea can harm health. In this work, covalent organic framework (COF) TpBD-(OH)₂ coating was fabricated for solid-phase microextraction (SPME) of O-PAHs. The coating contains abundant benzene rings and hydrogen bonding sites (oxygen and nitrogen groups). Density functional theory calculations, electrostatic potential distribution and X-ray photoelectron spectroscopy analysis indicated the COF efficiently adsorbs O-PAHs via van der Waals force, hydrogen bonding, electrostatic force, size matching, and π-π interaction. Under the best SPME conditions, a method for detecting O-PAHs in tea infusions was developed using gas chromatography-tandem mass spectrometry (GC-MS/MS). The method possessed low limit of detection (0.5-1.0 ng L^-1), wide linearity (2.0-1000.0 ng L^-1) and satisfactory recoveries (82.5 %-117.5 %). Furthermore, the method was used to study the impacts of different roasting methods on O-PAHs contamination, and results showed carbon roasting posed a higher risk.