Development and validation of a (semi-)quantitative UHPLC-MS/MS method for the determination of 191 mycotoxins and other fungal metabolites in almonds, hazelnuts, peanuts and pistachios

A multi-target method for the determination of 191 fungal metabolites in almonds, hazelnuts, peanuts and pistachios was developed. The method includes all mycotoxins regulated in the European Union and mycotoxins regularly found in food. After extraction with an acidified acetonitrile water mixture, the raw extract was diluted and injected directly into the UHPLC-MS/MS system. In two chromatographic runs, analysis was performed in positive and in negative ionisation mode. The method was in-house validated for the most important 65 analytes in these four commodities. Apparent recoveries between 80 and 120% were obtained for about half of the analyte-matrix combinations. Good repeatabilities (standard deviations < 10%) were achieved for the vast majority (83%) of all cases. Only in 6% of all combinations did the standard deviations exceed 15%. Matrix effects, arising during electrospray ionisation, significantly influenced the determination. For instance, signal suppression was observed for several early-eluting analytes and also signal enhancement up to 295% for physcion in peanuts was determined. Concerning extraction recovery, 94% of the analyte-matrix combinations showed values higher than 50%. Lower limits of quantification ranged between 0.04 μg kg(-1) for enniatin B3 in peanuts and 500 μg kg(-1) for HC toxin in hazelnuts. Additionally, the applicability of the developed method was demonstrated through the analysis of 53 naturally contaminated nut samples from Austria and Turkey. Overall, 40 toxins were quantified; the most frequently found mycotoxins were beauvericin (79%), enniatin B (62%) and macrosporin (57%). In the most contaminated hazelnut sample, 26 different fungal metabolites were detected.