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Knowledge about the contamination of cereals with mycotoxins produced by the fungusAlternaria is rare in Germany. With regard to the fact thatAlternaria spp. were detected in the leaves and in the ears of winter wheat in high frequency and high numbers a monitoring program was started in order to get more information about the actual contamination of winter wheat with the three importantAlternaria-mycotoxins: Alternariol (AOH), alternariol monomethyl ether (AME) and tenuazonic acid (TeA). In 2000 and 2001 the occurrence ofAlternaria spp and their toxins in kernels and straw of winter wheat harvested in the state of Brandenburg (Germany) was investigated. First, for the sensitive determination of theAlternaria mycotoxins a HPLC method has been developed. Sample preparation included the extraction with acetonitrile/KCI and the purification by a liquid/liquid partition step. The toxins were analysed by HPLC with fluorescence (AOH, AME) or UV/VIS (TeA) detection after separation through a C18 column using methanol + water + zinc sulphate as eluent. AME and TeA were only detected in few kernel probes in concentrations of 45-83 ppb (AME) and 44-105 ppb (TeA), respectively. 50% of the straw probes were highly contaminated with TeA (300 ppb-75 ppm).