Collaborative Study Report: Determination of Alternaria toxins in cereals, tomato juice and sunflower seeds by liquid chromatography tandem mass spectrometry

Abstract

The Institute for Reference Materials and Measurements of the Joint Research Centre, a Directorate-General of the European Commission, organised a method validation study to evaluate the performance of a method for the simultaneous determination of five Alternaria toxins in cereals, tomato juice and sunflower seed samples. The method validation study was conducted according to the International Union for Pure and Applied Chemistry harmonised protocol. The method was used for the determination of altenuene, alternariol, alternariol monomethyl ether, tentoxin and tenuazonic acid in both naturally contaminated and fortified samples. It was based on the extraction of the test materials with an acidified methanol – water mixture, followed by solid phase extraction clean-up. The determination was carried out by reversed phase high performance liquid chromatography coupled to a triple quadrupole mass spectrometric detector. The trial involved 16 participants representing a cross section of research, private and official control laboratories from 11 EU Member States and Canada. The selection of collaborators was based on the performance in the pre-trial that was organised prior to the collaborative trial with participation of 25 laboratories. Mean recoveries reported ranged from 53% to 107%. The sample reconstitution in a water-based injection solution is thought to be responsible for the low recovery obtained for alternariol monomethyl ether, which is the least polar compound from the toxins of interest. The relative standard deviation for repeatability (RSDr) ranged from 2.0 to 34.8%. The relative standard deviation for reproducibility (RSDR) ranged from 7.7 to 49.6%, reflecting HorRat values from 0.5 to 2.4 according to the Horwitz function modified by Thompson. A correction for recovery with the data generated by spiking experiments partially improve the reproducibility performance of the method. The results highlight that the performance characteristics strongly depend on the matrix analysed, despite that fact that matrix matched calibration was used. These matrix effects can be compensated using stable isotope labelled internal standards; however, stable isotope analogues for the analysed compounds are not commercially available so far. The outcome of this study however underpins its fitness-for-purpose, which is a requirement for its formal standardisation by the European Committee for Standardization (CEN).JRC.F.5 - Food and Feed Complianc