Determination of ochratoxin A in licorice extract based on modified immunoaffinity column clean-up and HPLC analysis

Contamination of ochratoxin A (OTA) is a common concern for the quality and safety of licorice and its derivatives, while their complex sample matrices always restrict the monitoring and regulation of OTA. Taking the much more concentrated and complicated licorice extract as the representative, a modified analysis method was established for OTA by HPLC. Parameters were comprehensively investigated based on liquid-liquid extraction and immunoaffinity column clean-up. In comparison to other methods, the developed method achieved effective clean-up efficiency and selectivity without tedious procedures and specialized instrumentation. Good linearity (R2 ≥0.9995), low LOD/LOQ (0.10 μg/kg/0.33 μg/kg), and satisfactory recovery (90.0%-96.4%, RSDs <7.0%) indicated the satisfactory sensitivity and reliability of the method. In addition, the applicability and robustness of the method was demonstrated by the analysis of large numbers of licorice extract samples. It is noteworthy that 66.5% of 176 samples were contaminated with OTA, while the concentrations of 9.1% of samples exceeded the maximum limit (ML, 80 μg/kg) defined by the EU. On account of the high contamination frequency and broad concentration range of OTA, the daily intake limit of licorice extract was preliminarily determined to be 123.18-123.93 g/day (chronic exposure) and 24.24 g/day (acute exposure), indicating a potential of acute risk through daily exposure. This calls for improved supervision and regulation for OTA contamination in licorice samples. This study suggests a prospective option for the efficient determination and routine monitoring of OTA in licorice and its derivatives, simultaneously providing a valuable data base for its health risk assessment.