Headspace solid-phase microextraction of semi-volatile ultraviolet filters based on a superhydrophobic metal-organic framework stable in high-temperature steam.

Headspace solid-phase microextraction (HS-SPME) of low volatile analytes from complex aqueous samples can be substantially facilitated by elevating the temperature of the samples. However, many SPME coatings prepared from novel sorptive materials may suffer from low stabilities in hot water steam. Herein, a superhydrophobic metal-organic framework (MOF) derived from decorating the metal-oxo nodes of the amino-functionalized UiO-66(Zr) with phenylsilane was prepared and successfully developed into a novel SPME fiber coating. The highest extraction efficiencies towards the semi-volatile ultraviolet (UV) filters were achieved when the aqueous samples were heated up to 100 °C. It was notable that the lab-made coating exhibited extraordinary stability towards hot water steam, probably because the hydrophobic groups capped on the MOF prevented water molecules from entering and deconstructing its lattice. Even after being treated with water steam under 100 °C for 21 h, the extraction performance of the coating remained unchanged, and the crystal structure of the MOF maintained. Furthermore, a negligible matrix effect was observed even in the samples containing humic acid. Under the optimal extraction and thermal desorption conditions, a method for determining UV filters in aqueous samples was established, which possessed low detection limits (0.6-2.1 ng L), wide linear ranges (10-50000 ng L), good inter-fiber reproducibility (2.3-6.0%, n = 6), and satisfying intra-fiber repeatability (1.8-5.8%, n = 3). The method was successfully applied in quantifying UV filters in environmental water samples. In addition, the lab-made NH-UiO-66(Zr)-shp-coated fiber was also suitable for the analysis of polycyclic aromatic hydrocarbons (PAHs). This study provided an effective strategy for preparing MOF coatings that can maintain their crystalline structures and high extraction performances in high-temperature steam.