Lijalem Yared Getachew (KRISS)

Kihwan Choi (KRISS)

Byungjoo Kim (KRISS)

Lijalem Yared Getachew (KRISS)

Hyeonwoo Yu (KRISS)

Kihwan Choi (KRISS)

Byungjoo Kim (KRISS)

An analytical method based on isotope dilution-ultrahigh-performance liquid chromatography-tandem mass spectrometry (ID-UHPLC-MS/MS) was established for the accurate determination of Aflatoxins (AFs) B₁, B₂, G_1, and G₂ in raw coffee bean, roasted coffee bean, and instant coffee. Uniformly labeled ¹³C- analogues of AFs were used as internal standards. Initially, a mixture of water/methanol (20/80, v/v) was used as the extraction solvent due to its high recoveries for all AFs. However, the sample extract after cleanup using immunoaffinity columns shows substantial matrix interferences, resulting in a bias in isotope ratio measurement. Therefore, a mixture of water/methanol (50/50, v/v) was selected for accurate isotope ratio measurement with adequate elimination of matrix interferences. The proposed method showed excellent accuracy (97% –103%) for all AFs over the concentration range of (0.5– 4) µg/kg, with the interday and intraday precision of less than 6%. Moreover, the measurement uncertainty was below 5%. (with a 95% confidence level).

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