Vitamin B12 This page summarizes the optical absorption and emission data of Vitamin B12 that is available in the PhotochemCAD package, version 2.1a (Du 1998, Dixon 2005). I reworked their data to produce these interactive graphs and to provide direct links to text files containing the raw and manipulated data. Although I have tried to be careful, I may have introduced some errors; the cautious user is advised to compare these results with the original sources.

You can resize any of the graphs by clicking and dragging a rectangle. If you hover the mouse over the graph, you will see a pop-up showing the coordinates. One of the icons in the upper right corner will let you export the graph in other formats.


This optical absorption measurement of Vitamin B12 were made by R.-C. A. Fuh in the summer of 1995 using a Cary 3. The absorption values were collected using a spectral bandwidth of 1.0 nm, a signal averaging time of 0.133 sec, a data interval of 0.25 nm, and a scan rate of 112.5 nm/min.

These measurements were scaled to make the molar extinction coefficient match the value of 27,500cm-1/M at 361.0nm (Hill, 1964).

Original Data | Extinction Data


For absorption data, also see (Pratt, 1966). No significant fluorescence emission is observed except from the benzimidazole unit at 303 nm (Fugate, 1976). The fluorescence spectrum was not collected.


Dixon, J. M., M. Taniguchi and J. S. Lindsey (2005), "PhotochemCAD 2. A Refined Program with Accompanying Spectral Databases for Photochemical Calculations, Photochem. Photobiol., 81, 212-213.

Du, H., R.-C. A. Fuh, J. Li, L. A. Corkan and J. S. Lindsey (1998) PhotochemCAD: A computer-aided design and research tool in photochemistry. Photochem. Photobiol. 68, 141-142.

Fugate, R. D., C.-A. Chin and P.-S. Song (1976) A spectroscopic analysis of vitamin B12 derivatives. Biochim. Biophys. Acta 421, 1-11.

Hill, J. A., J. M. Pratt and R. J. P. Williams (1964) The chemistry of vitamin B12. Part I. The valency and spectrum of the coenzyme. J. Chem. Soc. (London) 5149-5153.

Pratt, J. M. and R. G. Thorp (1966) The chemistry of vitamin B12. Part V. The class (b) character of the cobaltic ion. J. Chem. Soc. A, 187-191.