Multiclass mycotoxin analysis in Silybum marianum by ultra high performance liquid chromatography-tandem mass spectrometry using a procedure based on QuEChERS and dispersive liquid-liquid microextraction

Ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) has been proposed for the determination of 15 mycotoxins in milk thistle (Silybum marianum), including aflatoxins, fumonisins, trichothecenes, ochratoxin A, citrinin, sterigmatocystin and zearalenone. The mycotoxins were detected by electrospray ionization in positive ion mode and multiple reaction monitoring (MRM), achieving the separation in about 4 min. Sample treatment consisted of a modified method based on a first step using a QuEChERS-based procedure which allowed the determination of fumonisin B, fumonisin B-2, nivalenol, deoxynivalenol and fusarenon-X, and a subsequent clean-up based on dispersive liquid-liquid microextraction (DLLME) for the determination of the rest of mycotoxins. The method has been validated in extract and seeds of milk thistle, obtaining limits of quantification lower than those usually permitted by legislation in food matrices, with precisions lower than 10%. Recoveries were between 62.3% and 98.9%, except for zearalenone in seeds samples and citrinin in extract. The method was also applied for studying the occurrence of these mycotoxins in market samples (six samples of seeds, three of them purchased in bulk in a street vendor, and one natural extract of milk thistle), and HT-2, T-2 and zearalenone have been found in some of the samples. To the best of our knowledge, this is the first time that this type of treatment has been used for these complex food matrices, allowing the analyses of the most important mycotoxins. (C) 2013 Elsevier B.V. All rights reserved.