Isotope dilution LC-MS/MS for the quantification of ergot alkaloids: a comparative study

Ergot alkaloids (EAs) are toxic secondary metabolites formed by various fungi, most notably Claviceps purpurea, which infects cereal crops such as rye, wheat, and barley. Due to their toxicity, the European Commission established maximum levels for 12 priority EAs in cereals and related products in 2022. Routine monitoring, typically employing high-performance liquid chromatography coupled to tandem mass spectrometry, is challenged by the unavailability of isotope-labeled internal standards. To address this, we previously synthesized internal standards (ISTDs) for 12 priority EAs and herein we evaluate their performance through an interlaboratory comparison against the standard addition approach prescribed in EN 17425. The ISTDs significantly improved method precision and trueness, with results in good agreement across both laboratories. Furthermore, we developed a reference material for EAs in rye flour, in accordance with ISO 33405 guidelines, using stable isotope dilution mass spectrometry as primary method. This internal RM contributes to safer foodstuffs by supporting reliable method development and validation for EAs.