Journal of Chromatography A (2008), 1206, 2, 89--94 DOI: 10.1016/j.chroma.2008.07.091
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.