Comparison of a Microbiological Assay and a Fully Automated Chemiluminescent System for the Determination of Vitamin B12 in Food

A fully automated chemiluminescence analyzer for the determination of vitamin B12 in serum has been commercialized and clinically used. To determine the applicability of this apparatus in food analysis, vitamin B12 was assayed in foods by the chemiluminescent method, which was compared with a microbiological method. In shellfishes and spirulina, the values determined by the microbiological method were ∼6−8-fold greater than the values determined by the chemiluminescence method, although there was good similarity between the values by the two methods in other foods. Except for the shellfishes and spirulina, which contained substantial amounts of vitamin B12-substitutive compounds or inactive vitamin B12 analogues (or both), the observed correlation coefficient between the methods in the foods tested was excellent (r = 0.99, y = 1.2x − 1.1, n = 9). The chemiluminescence method was suitable for the determination of vitamin B12 in foods as well as in serum and was simpler (fully automated) and more rapid (180 samples analyzed per hour), highly selective (use of intrinsic factor, the most specific vitamin B12-binding protein), and reproducible (coefficients of variation of 1.2−6.7%) than the microbiological method. Keywords: Vitamin B12; bioassay; chemiluminescence; intrinsic factor; food