A UHPLC/UV method was developed and validated for the determination of human active vitamin B12 in cell extracts of Propionibacterium freudenreichii subsp.  As confirmed by UHPLC-MS, the active vitamin B12 could be separated from pseudovitamin B12. 
UHPLC
An Acquity HSS T3 C18 column resulted in a baseline separation, a calibration curve of excellent linearity and a low limit of detection (0.075 ng/5 μL injection). 
Acquity HSS T3 C18 column
As confirmed by UHPLC-MS, the active vitamin B12 could be separated from pseudovitamin B12. 
UHPLC-MS