Spectral study of photolysis of aqueous cyanocobalamin solutions in presence of vitamins B and C.
The UV and visible absorption characteristics of B and C vitamins have been studied in the pH range 2.0-7.0. The overlapping of the absorption bands of thiamine hydrochloride, nicotinamide, pyridoxine hydrochloride and ascorbic acid with cyanocobalamin in the UV region and those of riboflavin in the UV and visible region may influence the rate of photolysis of cyanocobalamin in aqueous solution due to mutual interaction on exposure to light. The spectral variations in cyanocobalamin solutions at pH 2.0-7.0 containing appropriate amounts of the individual B/C vitamins, during photolysis, have been monitored and the effect of pH on the rates of reaction has been discussed. The rates of photolysis, in general, decrease with an increase in pH probably due to gradual deprotonation of cyanocobalamin cation (B12 H+) as indicated by the magnitude of absorbance loss at the maxima at 361 and 550 nm.
Ansari
Izhar A
IA
Rafiquee Shaheed Employees Hospital, Karachi, Pakistan.
Vaid
Faiyaz H M
FH
Ahmad
Iqbal
I