Determination of Total Aflatoxins in Polished Rice by Liquid Chromatography-Fluorescence Detection with Multifunctional Column Cleanup and Precolumn Derivatization: Single-Laboratory and Inter-Laboratory Validation Studies.

Background: Aflatoxins (AFs) are toxic metabolites produced by Aspergillus spp. Because AFs are potent carcinogens in humans and animals, many countries have set regulatory limits for AFs in foods to prevent dietary exposure. From a global food safety perspective, in 2023, the Codex Alimentarius Commission established the maximum level (ML) of total AFs in certain cereals and cereal-based products, including polished rice. Therefore, validated analytical methods for AFs detection are necessary.

Objective: In this study, an HPLC-fluorescence method coupled with multifunctional column cleanup and trifluoroacetic acid derivatization was developed for the determination of AF levels in polished rice.

Methods: Our method was validated in a single-laboratory study using AF-spiked materials, followed by an inter-laboratory validation study. Twelve laboratories participated in the inter-laboratory validation study, and five polished rice test samples artificially contaminated with AFs were analyzed.

Results: In a single-laboratory study, the ranges of mean recoveries of AF B1, B2, G1, G2, and total AFs were 101, 100-103, 93-96, 95-98, and 97-99%, respectively. The RSDs for within-day and between-day variations were all ≤4.4%. In the inter-laboratory validation study, the RSDs for repeatability and reproducibility were from 0.7 to 2.7% and 3.3 to 8.9% for all analytes, respectively.

Conclusion: In response to the Codex ML and method performance criteria for AFs in polished rice, an analytical method based on HPLC-fluorescence detection was developed. All method performance parameters estimated from the test results of the single-laboratory and inter-laboratory validation studies met the criteria required by the Codex.

Highlights: Single- and inter-laboratory studies for the validation of an analytical method for AF level determination in polished rice were successfully performed. This analytical method will be suitable to determine AF levels around the Codex ML set for polished rice.