Development of a corn flour certified reference material for the accurate determination of aflatoxins

A corn flour certified reference material (CRM), KRISS CRM 108-01-013, was developed to support accurate measurement of aflatoxins (AFs). Corn flour naturally contaminated with AFs was mixed with AF-free corn flour to obtain a material with representative contamination levels. The mixed material was freeze-dried, milled, sieved, and thoroughly homogenized, and then dispensed into units containing approximately 15 g and stored at - 70 °C. Characterization was carried out using a validated isotope-dilution ultra-high-performance liquid chromatography-tandem mass spectrometry reference measurement procedure. Low between-bottle variability was observed, with relative standard deviations of 1.6 %, 1.0 %, 0.8 %, and 0.9 % for aflatoxin B₁ (AFB₁), aflatoxin B₂ (AFB₂), aflatoxin G₁ (AFG₁), and aflatoxin G₂ (AFG₂), respectively. Short- and long-term stability studies confirmed the stability of the target AFs under the investigated conditions; AFB₁ and AFG₂ were stable at - 70 °C for up to 18 months, whereas AFB₂ and AFG₁ were confirmed for 6 months at the same temperature. The certified mass fractions were (2.334 ± 0.086) µg/kg for AFB₁ and (0.1332 ± 0.0040) µg/kg for AFG₂, whereas AFB₂ and AFG₁ were assigned indicative values of (0.351 ± 0.010) µg/kg and (0.684 ± 0.022) µg/kg, respectively, because sufficient evidence of metrological traceability to the SI units could not be established. This CRM provides a metrologically traceable tool for the determination of AFB₁ and AFG₂ and indicative values for AFB₂ and AFG₁, thereby supporting quality assurance and validation of AF quantification in corn.