Vitamin B12. III. The assay of vitamin B12

Abstract

1. 1. After the addition of KCN, purified liver-extracts can be chromatographed on Al2O3, the vitamin B12 being collected as one single band which can be measured spectrophotometrically.

2. 2. The values, thus obtained, agree satisfactorily with those of the L. Leichmannii and a little less with the L. lactis Dorner assay. both in liquid medium.

3. 3. In our hands the cup plate assay with L. lactis dorner proved less satisfactory, the slope of the dose-response curve being dependent on the purity of the sample under investigation.