Highly stable benzonitrile functionalized covalent organic framework coating for solid-phase microextraction of hydroxyphenyl esters in complex matrix samples.

A mesoporous surface benzonitrile functionalized covalent organic framework (TpBD-CN-COF) was synthesized as a novel solid-phase microextraction (SPME) fiber coating for the extraction of six hydroxyphenyl esters (PBs), and combined with gas chromatography-flame electric-ion detector (GC-FID). PBs were sensitively determined in aqueous solution. Due to its high specific surface area, high chemical stability in both strongly acidic and alkaline media, and in polar or non-polar media, as well as its high thermal stability, the TpBD-CN-COF fiber coating showed excellent extraction performances for PBs with an enrichment factor twice as high as that of TpBD-COF. Some parameters that influenced the extraction performance, such as extraction time and temperature, pH, and stirring speed were investigated. Under optimal conditions, a wide linear range (0.06-500 μg L), low limits of detection (LOD, 0.003-0.042 μg L) were obtained for PBs determination. The relative standard deviations (RSDs, n = 6) for intra-day, inter-day, and fiber-to-fiber were less than 8.06%, 7.8%, and 8.6%, respectively. Furthermore, the analytical method could be successfully used to detect six PBs in cosmetics and environmental water samples, achieving satisfactory recoveries ranging from 85.14 to 107.67%.