ANALYTICAL METHODS FOR THE DETERMINATION OF STERIGMATOCYSTIN IN CHEESE, BREAD AND CORN PRODUCTS USING HPLC WITH ATMOSPHERIC-PRESSURE IONIZATION MASS-SPECTROMETRIC DETECTION

Methods have been developed for the determination of sterigmatocystin in bread, maize and cheese using HPLC linked to mass spectrometry (MS) atmospheric pressure chemical ionization for detection and concurrent confirmation of sterigmatocystin at levels down to less than 5 mu g/k g. Candidate extraction methods were initially checked for recovery an d reproducibility by spiking commodities at a level of 200 mu g/kg of sterigmatocystin and using HPLC with post-column derivatization. Recov ery was found to be greater than 90% for bread and maize, and 75% for cheese. Mass spectrometer conditions for detecting sterigmatocystin we re established by injecting solutions directly into the mass spectrome ter. Extracts of bread, maize grits and cheese prepared by the candida te extraction methods were examined using HPLC/MS using samples spiked at a level of 20 mu g/kg of sterigmatocystin. Results for bread and m aize samples showed that the extraction procedure recovered more than 90% of added sterigmatocystin and produced extracts free of interferen ce from co-extractives, with limits of detection of less than 2 mu g/k g for both commodities. The HPLC/MS results for cheese extracts gave l ower average recoveries of 55%. These results were also more variable. However, the apparent limit of detection for sterigmatocystin in chee se was still about 4 mu g/kg.