A novel polyhedral oligomeric silsesquioxane-based hybrid monolith as a sorbent for on-line in-tube solid phase microextraction of bisphenols in milk prior to high performance liquid chromatography-ultraviolet detection analysis

•A novel polyhedral oligomeric silsesquioxane-based hybrid monolith was synthesized and used as extraction adsorbent of on-line in-tube SPME.•On-line in-tube SPME-HPLC method is simple, rapid and sensitive for the determination of four BPs in milk.•The poly (POSS-co-AM-co-EDMA) monolith was used to extract BPs via π-π, hydrophobic and hydrogen bond interaction.•The method shortened the whole analysis time and reduced the consumption of organic solvents. An on-line in-tube solid-phase microextraction (in-tube SPME) coupled with high-performance liquid chromatography (HPLC) method was proposed based on a novel polyhedral oligomeric silsesquioxane (POSS)-hybrid monolith for the determination of four bisphenols (BPs) in milk. The monolith was synthesized using acrylamide (AM) and monomethacrylate-functionalized POSS (mono-MA-POSS) as functional monomers to copolymerize with ethylene dimethacrylate (EDMA). Due to the abundant hydrogen bonding, π-π and hydrophobic interaction sites, the synthetic monolith displayed satisfying extraction performance for target BPs. Under the optimized conditions, the developed on-line in-tube SPME-HPLC method exhibited low limits of detection (LODs) (0.030–0.055 ng mL−1). The spiked recoveries were between 85.4 % and 111.8 %, and the relative standard deviations (RSDs) were less than 3.5 % for all the analytes. The results showed that the proposed method provided alternative for the analysis of BPs in complex samples.