Identification—
The absorption spectrum, in the range of 300 nm to 550 nm, of the solution employed for measurement of absorbance in the
Assay exhibits maxima at the same wavelengths as that of a similar solution of
USP Cyanocobalamin RS, concomitantly measured, and the ratio
A361/
A550 is between 3.15 and 3.40.
Assay—
Dilute, if necessary, an accurately measured volume of Injection, equivalent to not less than 300 µg of cyanocobalamin, quantitatively and stepwise with water to a concentration of about 30 µg per mL. Dissolve an accurately weighed quantity of
USP Cyanocobalamin RS in water, and dilute quantitatively and stepwise with water to obtain a Standard solution having a known concentration of about 30 µg per mL. Concomitantly determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 361 nm, with a suitable spectrophotometer, using water as the blank. Calculate the quantity, in µg, of C
63H
88CoN
14O
14P in each mL of the Injection taken by the formula:
10(C/V)(AU / AS),
in which
C is the concentration, in µg per mL, of
USP Cyanocobalamin RS in the Standard solution;
V is the volume, in mL, of Injection taken; and
AU and
AS are the absorbances of the solution from the Injection and the Standard solution, respectively.
85
—
It contains not more than 0.4 USP Endotoxin Unit per µg of cyanocobalamin.