Polyhedral oligomeric silsesquioxane hybrid monolithic microcartridges for the determination of β-lactoglobulin in food by on-line solid-phase extraction capillary electrophoresis-mass spectrometry

• POSS-MA monolithic columns were easily prepared to cut plug-and-play microcartridges. • A POSS-MA-SPE-CE-MS method was developed for β-LG analysis. • LODs were 100 times lower than with CE-MS. • A low LOD of 0.1 μg·mL −1 enables detection of allergen threshold levels in food. • POSS-MA-SPE-CE-MS provides cost-effective, sensitive, and reliable protein analysis. A novel polyhedral oligomeric silsesquioxane methacryl substituted (POSS-MA) monolithic microcartridge was prepared for the determination of low levels of the allergenic protein β-lactoglobulin (β-LG) in food by on-line solid-phase extraction capillary electrophoresis-mass spectrometry (SPE-CE-MS). The material was synthesized inside a 250 μm inner diameter (i.d.) capillary column by free radical polymerization using a simple "one-pot" method. This capillary column was subsequently cut and straightforwardly assembled as microcartridges connected in-line with 75 μm i.d. separation capillaries for SPE-CE-MS. Several SPE-CE-MS parameters (such as loading time, type of eluent, or time and pressure of elution) were optimized using an acidic background electrolyte (BGE) composed of 2 M acetic acid (HAc, pH 2.2). Under optimized conditions, the protein sample was loaded at 930 mbar for 20 min ( ca . 110 μL), followed by a washing step with BGE at 930 mbar for 1 min, and finally eluted with 2 M HAc in methanol at 100 mbar for 60 s ( ca. 600 nL). The method exhibited linearity from 0.25 to 10 μg·mL −1 of β-LG, with a limit of detection of 0.1 μg·mL −1 , and a 100-fold increase in sensitivity compared to CE-MS. It was successfully applied to the determination of β-LG in dairy free white breads, yielding satisfactory results. These outcomes highlight the strong potential of the developed SPE-CE-MS method, using plug-and-play POSS-MA monolithic microcartridges, for precise food safety and quality control.