[Methods of determination of vitamin B 12]

A brief review on the methods for vitamin B12 determination is presented. The most appropriate utilization of each method based on its sensitivity, on the availability of the sample and on practical difficulties has been indicated. The methods have been divided into: a) physico-chemical methods, where the vitamin is identified spectrophotometrically; b) microbiological methods, where the vitamin is determined quantitatively by means of the growth of cobalamine dependent bacterial strains; c) kinetic methods, based on the different rate of conversion of the different cobalamines into dicyanocobalamine in the presence of an alkaline solution of cyanide; d) enzymatic methods, where activation of apodioldehydrase is used for the quantitative determination of adenosylcobalamine; e) chromatographic methods, where the separation of the cobalamines is obtained by chromatography and the quantitative determination is obtained by means of the growth of cobalamine-dependent bacterial strains (bioautography); f) radioisotopic methods where total cobalamines are determined quantitatively by measuring radioactivity after addition of (57Co)-CNCbl and a specific binder.