Abstract
Alternaria toxins (ATs) are frequently found contaminants in foodstuffs (e.g., alternariol), often reaching high concentrations (e.g., tenuazonic acid). They can spoil a wide variety of food categories (e.g., cereals, vegetables, seeds and drinks) and storage at fridge temperatures does not prevent the growth of Alternaria fungi. Therefore, reliable and validated analytical methods are needed to protect human health and to ensure a transparent and fair trade. This paper describes new technical features that improved a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the analysis of ATs in tomato, wheat and sunflower seeds. This analytical method should be simple to implement in different laboratories across the EU and thus be an attractive candidate for standardisation. The major element for improvement was the use of isotopically labelled internal standards, only recently commercially available, thereby reducing the sample handling and improving the accuracy of the results. In addition, the sample extraction and the solid-phase extraction (SPE) enrichment/clean-up were fine-tuned, whereas a more suitable analytical column (XSelect HSS T3) with improved selectivity was also employed. Overall, this method shows adequate precision (repeatability < 5.7% RSD; intermediate precision < 7.0% RSD) and trueness (recoveries ranging from 74% to 112%). The limits of quantification in wheat (the most analytically demanding matrix) vary between 0.19 and 1.40 µg/kg. These figures were deemed satisfactory by the European Committee for Standardization (CEN) and have formed the basis for a subsequent interlaboratory validation study. The corresponding standard was published by CEN in 2021.
Highlights
Alternaria toxins (ATs) have gained attention as a potential health risk due to their mutagenicity, cytotoxicity and genotoxicity and can be classified as emerging mycotoxins [1,2]
This paper describes new technical features that improved a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the analysis of ATs in tomato, wheat and sunflower seeds
The precision of the method was evaluated as repeatability and intermediate precision analysing blank wheat, tomato and sunflower matrices spiked at the following levels: 100 μg/kg for tenuazonic acid (TeA); 10 μg/kg for ALT, AOH and alternariol monomethyl ether (AME); and 50 μg/kg for TEN
Summary
Alternaria toxins (ATs) have gained attention as a potential health risk due to their mutagenicity, cytotoxicity and genotoxicity and can be classified as emerging mycotoxins [1,2]. The open sandwich enzyme-linked immunosorbent assay (OS-ELISA) developed by Liang et al [31] demonstrated high sensitivity and specificity and is inherently a rapid and portable test, it lacks multi-toxin recognition and confirmation capabilities To tackle these drawbacks, Tsagkaris et al [33] proposed the use of the direct analysis in real time ion source coupled to orbitrap mass spectrometry (DART-Orbitrap MS), affording both screening and quantification/confirmatory abilities. This manuscript presents the approaches used to improve the precision and trueness of the method, taking advantage of the latest technical developments and available consumables It focuses on (i) the implementation of a superior HPLC separation of all ATs after eliminating the pre-column derivatisation of TeA; (ii) the optimisation of the sample extraction and SPE enrichment/clean-up applied to cereals, tomato products and sunflower seed samples (peeled and unpeeled); and (iii) the quantification of the ATs using an isotope dilution mass spectrometry (IDMS) approach employing all corresponding isotopically labelled internal standards
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