Simultaneous determination and occurrence of zearalenone and 12 modified forms in marketed foods using a validated LC-MS/MS method.

Modified forms of zearalenone (ZEN) may substantially contribute to overall dietary exposure but remain poorly characterized because of the limited availability of validated multi-analyte methods and occurrence data. In this study, we developed and validated a solid-phase extraction (SPE)-based LC-MS/MS method for the simultaneous determination of ZEN and 12 modified forms. We applied this method to characterize the occurrence and co-occurrence of these compounds in 330 commercially available food samples collected in South Korea. The method showed satisfactory analytical performance, with coefficients of determination (R2) between 0.996 and 1.000, limits of detection of 0.34-1.75 μg/kg, recoveries of 73-114%, and precision below 18% relative standard deviation (RSD). Overall, 16.7% of the samples contained at least one target analyte. ZEN was the predominant contaminant, detected in 15.2% of samples, whereas modified forms were detected in 5.8% of samples. Sorghum, Job's tears, and maize showed the highest frequencies and concentrations. Among the modified forms, α-zearalenol and ZEN-14-sulfate were the most frequently detected. Co-occurrence analysis showed that the parent and modified forms mainly occurred as binary combinations. Together with the preliminary exposure assessment, these findings indicate that monitoring parent ZEN alone may not fully characterize ZEN-related contamination and exposure, highlighting the need to include modified forms in future monitoring frameworks.