Preparation and characteristics of high pH-resistant sol–gel alumina-based hybrid organic–inorganic coating for solid-phase microextraction of polar compounds

A novel alumina-based hybrid organic–inorganic sol–gel coating was first developed for solid-phase microextraction (SPME) from a highly reactive alkoxide precursor, aluminum sec-butoxide, and a sol–gel-active organic polymer hydroxyl-terminated polydimethylsiloxane (OH-TSO). The underlying mechanism was discussed and confirmed by IR spectra. The porous surface structure of the sol–gel coating was revealed by scanning electron microscopy. A detailed investigation was conducted to evaluate the remarked performance of the newly developed sol–gel alumina–OH-TSO hybrid materials. In stark contrast to the sol–gel silica-based coating, the alumina-based coating demonstrated excellent pH stability. In addition, good thermal resistance and coating preparation reproducibility are also its outstanding performance. As compared to silica-based hybrids material, the ligand exchange ability of alumina makes it structurally superior extraction sorbents for polar compounds, such as fatty acids, phenols, alcohols, aldehydes and amines. Practical applicability of the prepared alumina–OH-TSO fiber was demonstrated through the analysis of volatile alcohols and fatty acids in beer. The recoveries obtained ranged from 85.7 to 104% and the relative standard deviation values for all analytes were below 9%.