Recent developments in stable isotope dilution assays in mycotoxin analysis with special regard to Alternaria toxins

Stefan Asam, Michael Rychlik

Stable isotope dilution assays (SIDAs) are becoming ever commoner in mycotoxin analysis, and the number of synthesized or commercially available isotopically labelled compounds has greatly increased in the 7 years since our last review dealing with this topic. Thus, this review is conceived as an update for new applications or improvements of SIDAs for compounds discussed earlier, but the main focus is on newly introduced labelled substances and the development of SIDAs for, for example, fusarin C, moniliformin or the enniatins. Mycotoxin research has concentrated on the emerging group of Alternaria toxins in recent years, and a series of SIDAs have been developed, including ones for tenuazonic acid, alternariol, altertoxins and tentoxin that are discussed in detail in this review. Information about synthetic routes, isotopic purity and mass-spectrometric characterization of labelled compounds is given, as well as about the development and validation of SIDAs and their application to foods, feeds or biological samples. As the number of commercially available labelled standards is increasing continuously, a general tendency for the use of analytical methods based on liquid chromatography coupled with mass spectrometry capable of identifying a series of mycotoxins simultaneously ("multimethods") and using one or more labelled internal standards can be observed. An overview of these applications is given, thus demonstrating that SIDAs are increasingly being used in routine analysis.