Selective and rapid immunomagnetic bead-based sample treatment for the liquid chromatography–electrospray ion-trap mass spectrometry detection of Ara h3/4 peanut protein in foods

Complex matrices commonly affect the sensitivity and selectivity of liquid chromatography–mass spectrometry (LC–MS) analysis. Thus, selective sample enrichment strategies are useful particularly to analyze organic biomarkers present in low abundance in samples. A selective immunomagnetic extraction procedure to isolate trace peanut allergen protein Ara h3/4 from breakfast cereals combined with microwave-assisted tryptic digestion and liquid chromatography–electrospray ion-trap tandem mass spectrometry (LC–ESI-IT-MS/MS) measurement was developed. Using protein A-coated magnetic bead (MB) support, anti-Ara h3/4 monoclonal antibodies (Abs) were used as selective capture molecules. The results obtained by LC–ESI-IT-MS/MS in terms of limit of detection (3 mg peanuts/kg matrix) and a significantly reduced matrix effect demonstrated that the Ab-coated magnetic bead was very effective to selectively trap Ara h3/4 protein in breakfast cereals. The magnetic bead-based sample treatment followed by LC–IT-MS/MS method here developed can be proposed as very rapid and powerful confirmatory analytical method to verify the reliability of enzyme-linked immunosorbent assay (ELISA) screening methods, since the magnetic bead-LC–IT-MS/MS method combines good sensitivity to the identification capabilities of mass spectrometry.