Improved method for measuring vitamin B12in serum using intrinsic factor,57CoB12, and coated charcoal

Abstract

An improved and simplified method is described for the measurement of vitamin B₁₂ in serum using intrinsic factor, ⁵⁷CoB₁₂, and coated charcoal. The extraction of serum in the presence of cyanide and the incorporation of B₁₂-deficient serum into the intrinsic factor control has increased the accuracy of the method for both sera and crystalline B₁₂ solutions. There are interesting differences between the results obtained for some sera by the isotope and L. leichmannii methods and the reasons for these differences are discussed.