Determination of ochratoxin A in liquorice products using HPLC based analytical methods. Part I: proficiency test of methods commonly used by the confectionary industry.

A European proficiency test series was accomplished on behalf of the CAOBISCO (Association of the Chocolate, Biscuit and Confectionery Industries of the EU) expert group on ochratoxin A to assess the performance of laboratories in measuring ochratoxin A in samples of various liquorice products. In addition, the impact of the extraction type (mainly with or without the use of halogenated solvents) was to be evaluated. Four different test samples (two liquorice powders and two liquorice pastes) were tested for sufficient homogeneity and distributed to 15 laboratories in 8 countries in Europe. The results were analysed using standard proficiency testing statistical procedures and laboratories were awarded z-scores on the basis of their reported results. The overall evaluation of the results shows a distinct variation between the participating laboratories. Based on a target standard deviation (σ-value) taken from the Horwitz equation, of the 14 laboratories that reported results, satisfactory results (z-score: |Z| ≤ 2.0) were obtained by 60% and 27% of the laboratories, respectively, for the two liquorice powders and by 93% and 53% of the laboratories, respectively, for the two liquorice pastes. Approximately equal numbers of laboratories used extraction types with and without the use of halogenated solvents. ANOVA testing of the results indicates there was no evident trend using different extraction solvents.