Determination of cyanocobalamin by isotope dilution LC-MS/MS

- Precise quantitation of cyanocobalamin in supplements by liquid chromatography-tandem mass spectrometry.
- Quantitation at ultra-trace level.
- Use of a specific isotopically enriched internal standard produced in-house.
- Stable quadrupole isotope dilution is used.

Cyanocobalamin (CNCbl) is an active form of vitamin B12, commonly employed for the preparation of multivitamin supplements and fortified food. In this study, we present a novel analytical method for its determination based on stable isotope dilution liquid chromatography electrospray tandem mass spectrometry (ID LC-MS/MS). Isotopically enriched 13C15NCbl was synthesized in-house and used as internal standard. The method was validated using NIST SRM 3280 multivitamin reference material and by comparison with an independent methodology based on LC-ICPMS. The proposed method provided a detection limit of 57 pg/g and could be applied for the determination of trace level of CNCbl in multivitamin supplements with a relative standard uncertainty better than 3%. The novel ID LC-MS/MS is a primary ratio method that could become a reference for CNCbl determination in multivitamins and food supplements. The method was applied for the characterization of two NRC multivitamin tablet Certified Reference Material (CRM) candidates, VITA-1 and VITB-1 whose CNCbl levels were quantified as 2.64 ± 0.09 and 1.75 ± 0.12 μg/g, respectively.

292