This interlaboratory collaborative study evaluated the precision performance of a high-performance liquid chromatography (HPLC) method for the determination of AFB1, AFB2, AFG1, AFG2, and total aflatoxins (AFs) in naturally contaminated corn flour. Three naturally contaminated test materials representing different contamination levels were prepared, assessed for homogeneity and stability, and distributed to 11 participating laboratories. Each laboratory analysed the test items in triplicate under repeatability conditions using immunoaffinity column clean-up, post-column derivatization, and fluorescence detection. Participant results were statistically screened by analyte and contamination level to identify censored measurements, outlying values, and inconsistent laboratory performance before calculation of the final precision parameters.
Precision estimates were obtained for AFB1, AFB2, and AFG1 at levels A and B, and for all four aflatoxins at level C. AFG2 could not be formally evaluated at levels A and B because the number of quantitative results was insufficient, mainly due to results reported as not detected or below the limit of quantification. Across the evaluable analyte–level combinations, repeatability coefficients of variation ranged from 3.17% to 10.25%, while reproducibility coefficients of variation ranged from 8.77% to 27.71%. Reproducibility variability was generally higher than repeatability variability, confirming the contribution of between-laboratory effects to total method variation. The results indicate that the HPLC method provided technically interpretable repeatability and reproducibility estimates for most analyte–level combinations in naturally contaminated corn flour, although low-level determination of AFG2 remained limited by analytical quantifiability.