Application of Ambient Ionization Mass Spectrometry to Detect the Mycotoxin Roquefortine C in Blue Cheese

Harmful secondary metabolites produced by fungi, mycotoxins, are found worldwide in a multitude of products. Roquefortine C (ROQ-C) is a mycotoxin produced by Penicillium roqueforti, the major fungus used to ripen blue-veined cheeses. To facilitate the screening of cheeses for ROQ-C, a method based upon the ambient ionization technique of direct analysis in real time-mass spectrometry (DART-MS) was developed. The method involved extraction with acetonitrile/water, removal of interferences with a cleanup column, and application to test strips. Thermal desorption was used to facilitate volatilization and ionization of the ROQ-C. The limits of detection and quantitation were 0.011 and 0.036 µg/mL, respectively, equivalent to 0.06 µg/g and 0.18 µg/g in cheese. Average recoveries at concentrations from 0.5 to 5 µg/g ranged from 80.2 to 87.4%. The assay was validated as a screening assay, with a cut-off value of 0.31 µg/g and a t-statistic of 25.95 at this level, indicating a very low probability of false positives (p < .00001). Results from the DART-TD-MS method were compared to results from an LC-PDA-MS method for 64 naturally contaminated cheeses. The two methods were in good agreement, with r2 = 0.9152, suggesting that the DART-MS method can be used to screen for ROQ-C in blue cheeses.