Validation of analytical methods for determining mycotoxins in foodstuffs

Abstract

The European Union (EU) has established demanding regulatory limits for controlling aflatoxins B 1, B 2, G 1 and G 2, in cereals, nuts, nut products and dried fruit, aflatoxin M 1 in milk, and ochratoxin A in cereals. These limits are likely to be extended in the future to additional commodities and other mycotoxins. For enforcement purposes and in particular for resolving any disputes between parties, it is essential that validated methods are available, with performance characteristics that meet certain minimum criteria. As such methods were not available and had not previously been validated either for matrices of interest in Europe or at the low European limits compared to the USA, the EU funded a method-validation project to fulfil this requirement. Immunoaffinity column clean-up methods with HPLC determination were established for aflatoxins B 1, B 2, G 1 and G 2 in peanut butter, pistachios, fig paste and paprika, aflatoxin B 1 in baby food, aflatoxin M 1 in liquid milk, and ochratoxin A in roasted coffee and baby food. For patulin in apple juice and apple puree, solvent extraction and solid-phase clean-up HPLC methods were developed. To undertake collaborative studies, particular care was taken in preparation of naturally-contaminated test materials containing the toxins at levels close to regulatory limits and in demonstrating the homogeneity of batches of material. To ensure that participants in the validation exercise could follow the procedures to be tested, videos of the methods were prepared showing, in particular, any critical steps. Prior to undertaking the method validation, participants were invited to collaborative study workshops to ensure that they fully understood the methods and their role in the study. This care in planning and executing the collaborative studies led to impressive performance characteristics and adoption of six procedures by AOAC International as First Action Methods and seven methods by CEN as European standards. The valuable lessons learned in undertaking these validation exercises are now being put to further use in studies aimed at validating methods for mycotoxins in foodstuffs, which are appropriate for developing countries based on TLC as the end determination but use more modern sample clean-up techniques.