Determination of ochratoxin A in liquorice products using HPLC-based analytical methods. Part II: harmonised method and method validation study

On the basis of the outcome of an European proficiency test series conducted on behalf of the CAOBISCO (Association of the Chocolate, Biscuit and Confectionery Industries of the EU) expert group on ochratoxin A, a new harmonised method was developed for the analysis of ochratoxin A in liquorice extracts. This method works without the use of halogenated solvents because, as the proficiency test showed, an aqueous extraction solution can be used instead of, for example, chloroform, whose use is restricted in the EU. The main objective of this method validation study was to check the performance of this harmonised method. To carry out the method validation study, a set of three different test samples (one liquorice powder and two liquorice pastes) and a liquorice powder sample with an indicated range of ochratoxin A (a so-called sunshine sample) was distributed to 21 laboratories in ten countries throughout Europe and to one laboratory in the USA. The study was evaluated according to internationally recognised guidelines. In terms of its repeatability and reproducibility for determining ochratoxin A in liquorice extracts with a relative standard deviation for repeatability (RSD_r) of between 6.68 and 19.95 and a relative standard deviation for reproducibility (RSD_R) of between 17.39 and 29.08 the performance of the harmonised method was found to be in the accepted range of the EU directive for the analysis of mycotoxins in several foodstuffs.