Three-dimensional hydroxylated covalent organic frameworks for solid phase extraction of glucocorticoids in environmental water samples

It is challenging to achieve the highly sensitive detection of glucocorticoids at ultratrace levels because of the abundant hydrophilic groups in their molecules and the complexity of environmental water sample matrices. Here, a highly crystalline three-dimensional hydroxylated covalent organic frameworks (denoted by COF-301) with tetra(4-anilyl)methane (TAM) and 2,5-dihydroxyterephthalaldehyde (DHTA) as building units was constructed and proposed as adsorbent for solid phase extraction (SPE) of glucocorticoids. Theoretical studies were conducted to elucidate the potential adsorption mechanism of glucocorticoids on the COF-301. The COF-301 based SPE combined with liquid chromatography-tandem mass spectrometry provides a promising approach for the preconcentration and determination of glucocorticoids residue in water samples. Good linearity with a correlation coefficient exceeding 0.9988, low limits of detection ranging from 0.024 to 0.075 ng L-1 and relative standard deviations below 6.68% were achieved. The proposed method was successfully applied to analyze glucocorticoids residue in actual water samples, demonstrating the prospects of this method for the determination of trace glucocorticoids.