Design of a covalent organic framework composite material functionalized with ionic liquids as the efficient adsorbent for pipette tip solid phase extraction of bisphenols from beverages and tap water.

Bisphenols (BPs) are typical environmental endocrine disruptors with potential toxicity and health risks. It is urgent to develop sensitive analytical methods for their trace detection. In this work, a covalent organic framework composite material modified with ionic liquids (COF-IL) was gently synthesized through quaternization and Click reactions, and utilized as the packing adsorbent for pipette tip solid phase extraction (PT-SPE) of BPs from bottled beverages and tap water. For COF-IL, the BET surface area was determined to be 423.9837 m2·g-1 and the maximum adsorption capacity for four BPs increased from 111.11 mg·g-1 to 416.67 mg ·g-1. Due to the appropriate pore size of COF-IL and the integration of π-π conjugation, hydrogen bond interaction, polar and dipole interaction and dispersion interaction, the presented PT-SPE-HPLC method showed wide linear ranges (0.001-100 μg·L-1 for BPA, BPAF and BPZ, and 0.002-100 μg ·L-1 for BPAP, R2 ≥ 0.9953) and low limits of detection (0.00006-0.0006 μg·L-1) for BPs. The intra-day and inter-day RSDs were 0.57%-5.06% and 1.30%-4.28%, respectively. After 60 successive PT-SPE cycles, neither the recoveries of BPs nor the structure of COF-IL showed any significant changes. The developed method was further applied to cola, orange juice and tap water samples, achieving recoveries ranging from 72.76% to 119.13% with RSDs less than 6.03% and matrix effect ranging from 80.33% to 119.44%. Due to its simplicity, convenience, accuracy, and sensitivity, this sample preparation method could be used for detecting and monitoring BPs residues in bottled beverages and tap water.