Stabiliiy of cyanocobalamin solutions insunlight and artificial light

A comparison of the degradation of cyanocobalamin (vitamin B(12)) solutions on exposure to sunlight and artificial light has been made using two concentrations, i.e. 950 mug/ml (corresponding to parenteral solutions) and 95 mu/ml (1:10 dilution) at pH 4.0, 5.5 and 7.0. Cyanocobalamin and the photoproduct, hydroxocobalamin (vitamin B(12b)), have been determined by a two component spectrophotometric method at 550 and 525 nm. Cyanocobalamin loss (950 mug/ml and 95 mug/ml) on exposure to sunlight for 2 hours amounts to 14.7-21.0% and 56.3-81.5% respectively indicating that light intensity is the rate determining factor in the reaction. In artificial light for 2 hours B(12) (950 mug/ml and 95 mug/ml) loses 2.7.19.4% and 1.5-27.7% respectively. Thus B(12) degradation in sunlight is greater compared to that of the artificial light, with the formation of some oxidation products, in addition to B(12b).