Simultaneous determination of six major ergot alkaloids and their epimers in cereals and foodstuffs by LC–MS–MS

摘要

This paper describes a new and rapid method for accurate quantification of the six ergot alkaloids, ergometrine, ergotamine, ergosine, ergocristine, ergocryptine, and ergocornine, by liquid chromatography–tandem mass spectrometry (LC–MS–MS). The six ergot alkaloids studied have been defined by the European Food Safety Authority (EFSA) as among the most common and physiologically active ones. In addition, the method enables the quantification of the corresponding six epimers (ergo-inines) of these ergot alkaloids. This is of considerable importance in terms of the differences in toxicity of the isomeric forms. The method involves extraction under alkaline conditions using a mixture of acetonitrile and ammonium carbonate buffer followed by a rapid clean-up using dispersive solid-phase extraction with PSA (primary secondary amine) and a short chromatographic LC-run (21 min) with subsequent MS–MS detection. The method was developed and validated using ten different cereal and food samples. The major strength of the new method compared with previously published techniques is the simplicity of the clean-up procedure and the short analysis time. The limits of quantification were 0.17 to 2.78 μg kg?1 depending on the analyte and matrix. Recovery values for the 12 ergot alkaloids spiked into ten different matrices at levels of 5, 50, and 100 μg kg?1 were between 69 and 105% for 85 of 90 recovery measurements made over six days. Measurement uncertainty values were highly satisfactory. At a concentration level of 5 μg kg?1 the expanded measurement uncertainty ranged from ±0.56 to ±1.49 μg kg?1, at a concentration level of 100 μg kg?1 the expanded measurement uncertainty ranged from ±8.9 to ±20 μg kg?1. Both LOQs and measurement uncertainties were dependent on the analyte but almost independent of the matrix. The method performance was satisfactory when tested in a mini-intercomparison study between three laboratories from three different countries.