유현우 (한국표준과학연구원)

최기환 (한국표준과학연구원)

김병주 (한국표준과학연구원)

유현우 (한국표준과학연구원)

최기환 (한국표준과학연구원)

김병주 (한국표준과학연구원)

We report the development of an isotope dilution liquid chromatography–tandem mass spectrometry method for the accurate determination of vitamin B₁₂ (cobalamin) in beef. Cobalamin forms were quantified after conversion to more stable cyanocobalamin (CN-Cbl) with KCN treatment using [¹³C₇]-cyanocobalamin as an isotope internal standard. Sample preparation conditions, including the amounts of beef and papain, the concentration of KCN, and the extraction time were optimized to improve conversion efficiency. Even under the optimized conditions, hydroxocobalamin (OH-Cbl) remained unconverted after KCN treatment, whereas adenosylcobalamin and methylcobalamin were below the limit of detection. The concentration of unconverted OH-Cbl was measured using added it to the CN-Cbl measurement result. The measured CN-Cbl and unconverted OH-Cbl concentrations ranged from 76.57 to 78.32 μg/kg and from 0.39 to 1.58 μg/kg, respectively, resulting in corrected total cobalamin concentrations of 77.33–78.75 μg/kg. The recovery of gravimetrically added CN-Cbl was 98.8%. The intra-day and inter-day relative standard deviations were 0.3–1.3% and 0.6%, respectively. The expanded relative uncertainties of the corrected total cobalamin results ranged from 1.70% to 2.61%.

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