Mixed matrix of MOF@COF hybrids for enrichment and determination of phenoxy carboxylic acids in water and vegetables

A novel mixed matrix of MOF@COF hybrid was firstly formed by coating of hexahedral cage structure MOF with lightweight porous COF, and applied in dispersive solid-phase extraction of the phenoxy carboxylic acids (PCAs) from water and vegetable samples. Combined with liquid chromatography-tandem mass spectrometry, an excellent method with low limits of detection (0.69-1.79 ng·L-1/0.002-0.006 ng·g-1), good reproducibility (1.32%-7.02%/1.81%-6.71%), and excellent linearities (10-1000 ng·L-1, R ≥ 0.9955/0.04-50 ng·g-1, R ≥ 0.9966) was established. The adsorption mechanisms deduced that the π-π interaction, hydrophobic effects, hydrogen bond, and halogen bond may promote the excellent adsorption of the PCAs. Finally, the applicability of the method was verified by spiking four kinds of water and vegetable samples with PCAs, and satisfying recoveries were obtained (between 83.3% and 104.9%).