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Issue 6, 2013
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A simple and sensitive LC-ICP-MS method for the accurate determination of vitamin B12 in fortified breakfast cereals and multivitamin tablets

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Abstract

A sensitive liquid chromatographic (LC) method coupled with inductively coupled plasma mass spectrometry (ICP-MS) has been developed for the determination of vitamin B12. The method was based on efficient isocratic separation with a mobile phase consisting of 20 mmol L−1 ethylenediaminetetraacetic acid (EDTA) in 25/75 methanolwater mixture (volume fractions) operating at a flow rate of 0.2 mL min−1. After LC separation, ionic cobalt (Co), cyanocobalamin, methylcobalamin, and hydroxocobalamin were measured as 59Co by ICP-MS. For Co as cyanocobalamin, the analyte of interest of this work, the method has shown good repeatability with relative standard deviation (RSD) of 3% for ten measurements and excellent linearity between 0.1 ng g−1 and 100 ng g−1 (linear regression, r2 > 0.999). The limit of detection (LOD) for cyanocobalamin was found to be less than 1 ng g−1, which permits the method to be employed for the determination of ultra-trace concentrations of vitamin B12 in various types of dietary supplements and fortified food products. Cyanocobalamin in aqueous solution was found to decompose under the ambient light of the laboratory; therefore, dark room conditions are required for the determination of vitamin B12 in the form of cyanocobalamin to minimize the photon-induced decomposition. To determine total Co in a commercial high-purity cyanocobalamin using direct ICP-MS measurement as part of an effort to characterize the chemical for use as a calibrant, it was observed that quantitative measurement of Co was achieved only through a complete acid digestion. The method was applied to the determination of vitamin B12 in Standard Reference Material (SRM) 3233 Fortified Breakfast Cereal. SRM 3280 Multivitamin/Multielement Tablet was used for quality assurance of the cereal sample measurements. The vitamin B12 value of (0.187 ± 0.016) mg kg−1 found in SRM 3233 was comparable to (0.219 ± 0.066) mg kg−1 obtained by Grocery Manufacturers Association's Food Industry Analytical Chemists Committee (FIACC) using microbiological assay. The (4.38 ± 0.05) mg kg−1 of vitamin B12 found in quality assurance samples of SRM 3280 was in good agreement with the certified values of (4.8 ± 1.0) mg kg−1.

Graphical abstract: A simple and sensitive LC-ICP-MS method for the accurate determination of vitamin B12 in fortified breakfast cereals and multivitamin tablets

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Publication details

The article was received on 26 Dec 2012, accepted on 10 Apr 2013 and first published on 10 Apr 2013


Article type: Paper
DOI: 10.1039/C3JA30383G
J. Anal. At. Spectrom., 2013,28, 901-907

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    A simple and sensitive LC-ICP-MS method for the accurate determination of vitamin B12 in fortified breakfast cereals and multivitamin tablets

    C. S. Kesava Raju, L. L. Yu, J. E. Schiel and S. E. Long, J. Anal. At. Spectrom., 2013, 28, 901
    DOI: 10.1039/C3JA30383G

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