Determination of masked mycotoxins using HPLC–tandem mass spectrometry

The topic of conjugated mycotoxins first caught the attention of investigators in the mid eighties of the last century because in some cases of mycotoxicoses, clinical observations in animals did not correlate with the low mycotoxin content determined in the corresponding feed. High performance liquid chromatography combined with tandem mass spectrometry offers a powerful tool for identification and characterization of polar non-volatile mycotoxin conjugates. Derivatives can be identified due to their molecular mass and their fragmentation behaviour. Moreover, known conjugates can be quantified and plant extracts can be screened for unknown mycotoxin conjugates with different MS/MS techniques. We chemically synthesized deoxynivalenol-3-β-D-glucopyranoside, deoxynivalenol-15-β-D-glucopyranoside and zearalenone-4-β-D-glucopyranoside. The two deoxynivalenol-glucosides showed different fragmentation behaviours on a hybrid quadrupole – linear ion trap tandem mass spectrometer and could therefore be distinguished. It was possible to confirm the identity of deoxynivalenol-3-glucoside in deoxynivalenol treated yeast, which expressed the Arabidopsis thaliana glucosyltransferase DOGT1. Furthermore, deoxynivalenol-3-glucoside was detected in deoxynivalenol treated Arabidopsis and wheat. We also confirmed the formation of ZON-4-glucoside, a substance that was already known to occur in contaminated wheat. Finally, we isolated and characterized zearalenone-4-sulfate from Fusarium inoculated rice.