Determination of ochratoxin A in licorice and licorice extracts by high-performance liquid chromatography coupled with fluorescence detection: collaborative study.

A collaborative study was conducted to validate an analytical method for the determination of ochratoxin A (OTA) in licorice (root powder) and licorice extracts (paste and powder). Contents of OTA ranged from 26 to 141 microg/kg and from 8 to 52 microg/kg for licorice extracts and root material, respectively. For the analysis, a test portion is extracted with a mixture of methanol and aqueous sodium bicarbonate solution. The extract is filtered and diluted with phosphate-buffered saline; and OTA is purified with an immunoaffinity column containing antibodies specific to OTA. The purified extract is dried, reconstituted, and quantified by HPLC with fluorescence detection. Twenty laboratories from 13 European Union member states, Uruguay, Turkey, and the United States of America participated in this study. The study was evaluated according to internationally accepted guidelines. The method performance characteristics can be summarized as follows: over a working range of 7.7 to 141 microg/kg OTA, the mean recoveries were 87% for licorice root and 84-88% for licorice extracts; and the RSDs for reproducibility ranged from 10 to 17% and from 11 to 22% in licorice extracts and licorice root, respectively. The method was found to be fit-for-purpose and to fulfill legal requirements as set in EC Regulation No. 401/2006.