Identification—
The absorption spectrum,in the range of 300nm to 550nm,of the solution employed for measurement of absorbance in the
Assayexhibits maxima at the same wavelengths as that of a similar solution of
USP Cyanocobalamin RS,concomitantly measured,and the ratio
A361/
A550is between 3.15and 3.40.
Assay—
Dilute,if necessary,an accurately measured volume of Injection,equivalent to not less than 300µg of cyanocobalamin,quantitatively and stepwise with water to a concentration of about 30µg per mL.Dissolve an accurately weighed quantity of
USP Cyanocobalamin RSin water,and dilute quantitatively and stepwise with water to obtain a Standard solution having a known concentration of about 30µg per mL.Concomitantly determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 361nm,with a suitable spectrophotometer,using water as the blank.Calculate the quantity,in µg,of C
63H
88CoN
14O
14Pin each mLof the Injection taken by the formula:
10(C/V)(AU/AS),
in which
Cis the concentration,in µg per mL,of
USP Cyanocobalamin RSin the Standard solution;
Vis the volume,in mL,of Injection taken;and
AUand
ASare the absorbances of the solution from the Injection and the Standard solution,respectively.