The Separation of Free and Bound Vitamin B12

S ummary . The separation of free and bound vitamin B₁₂ was studied using four binders and two forms of vitamin B₁₂ and effecting separation by charcoal adsorption, bag dialysis, ultrafiltration and gel filtration. In charcoal separation systems the results could be significantly affected by a change in the binder, the form of vitamin B₁₂, the type of charcoal, the mass of charcoal or the presence of albumin. In systems with gastric juice and cyanocobalamin one charcoal separation procedure yielded results which were comparable to those obtained by all other procedures but this did not occur with gastric juice and hydroxocobalamin or with other binders and both forms of vitamin B₁₂.
Results obtained using dialysis for separation varied with the membrane employed. Results obtained by gel filtration were significantly different from those obtained by ultrafiltration and those obtained by one ultrafiltration procedure were always significantly different from those yielded by another. Separation methods which give insignificantly different results in one system do not necessarily yield insignificantly different results in a system with a different binder or different form of vitamin B₁₂.