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

Abstract

A fully automated chemiluminescence analyzer for the determination of vitamin B 12 in serum has been commercialized and clinically used. To determine the applicability of this apparatus in food analysis, vitamin B 12 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 B 12 -substitutive compounds or inactive vitamin B 12 analogues (or both), the observed correlation coefficient between the methods in the foods tested was excellent ( r = 0.99, y = 1.2 x − 1.1, n = 9). The chemiluminescence method was suitable for the determination of vitamin B 12 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 B 12 -binding protein), and reproducible (coefficients of variation of 1.2−6.7%) than the microbiological method. Keywords: Vitamin B 12; bioassay; chemiluminescence; intrinsic factor; food