Comparison of methods for determination of vitamin B12 in microbial material

Three different methods for the measurement of vitamin B12 were compared: two spectrophotometric methods and an HPLC one. When the pure vitamin was used, the results obtained using all three methods were similar, but when samples from microbial material were used, the results were different. The HPLC method could distinguish the true vitamin B12 from the different vitamin B12 analogues whereas the spectrophotometric methods could not.