Specific activity:
not less than 0.02 MBq (0.5 µCi) per µg of cyanocobalamin.
Packaging and storage—
Preserve in tight containers, protected from light, and store in a cold place.
Labeling—
Label it to include the following: the date of calibration; the amount of 57Co as cyanocobalamin expressed as total megabecquerels (microcuries) and as megabecquerels (microcuries) per mL at the time of calibration; the amount of cyanocobalamin expressed in µg per mL; the name and quantity of the added preservative; the expiration date; and the statement “Caution—Radioactive Material.” The labeling indicates that in making dosage calculations, correction is to be made for radioactive decay, and also indicates that the radioactive half-life of 57Co is 270.9 days, and directs that the Oral Solution be protected from light.
Radionuclide identification (see Radioactivity 
821
)—
Its gamma-ray spectrum is identical to that of a specimen of
57Co of known purity that exhibits a major photopeak having an energy of 0.122 MeV.
Radiochemical purity—
Mobile phase—
Prepare a solution of 10.0 g of dibasic sodium phosphate in 1000 mL of water, and adjust with phosphoric acid to a pH of 3.5. Prepare a mixture of this solution and methanol (73.5:26.5), mix, and degas. Use within 2 days.
Test solution—
Use the Oral Solution.
Standard solution—
Transfer about 10 mg of cyanocobalamin, accurately weighed, to a 100-mL volumetric flask, dilute with Mobile phase to volume, and mix. Transfer 2.0 mL of this solution to a 100-mL volumetric flask, dilute with Mobile phase to volume, and mix.
Chromatographic system (see Chromatography 621)—
The liquid chromatograph is equipped with a 361-nm detector, a gamma detector adjusted for
57Co and a 4.6-mm × 25-cm stainless steel column that contains 5-µm packing L7. The flow rate is about 1 mL per minute.
Procedure—
Inject about 100 µL of the
Standard solution into the chromatograph, record the chromatogram for 30 minutes, and note the retention time of the cyanocobalamin peak. Inject 100 µL of the
Test solution into the chromatograph, and record the chromatogram for three times the retention time of cyanocobalamin. Measure the peak areas using the gamma detector, and calculate the percentage of cyanocobalamin present as cyanocobalamin
57Co in the portion of Oral Solution taken by the formula:
100(rU / rT),
in which
rU is the peak response for cyanocobalamin
57Co obtained from the
Test solution; and
rT is the total of all the peak area responses in the radiochromatogram obtained from the
Test solution. Not less than 90% of the total radioactivity is found as cyanocobalamin
57Co.
Radionuclidic purity—
Using a suitable calibrated instrument (see
Radioactivity 821 ) and standardized solutions of
58Co,
57Co, and
60Co, record the gamma spectrum of the Oral Solution. The spectrum does not differ significantly from that of the standardized
57Co solution. Determine the relative amounts of
58Co,
57Co, and
60Co present. Cobalt 58 has a half-life of 70.9 days, and its presence is shown by 0.511-MeV and 0.811-MeV gamma photons. Cobalt 60 has a half-life of 5.27 years, and its presence is shown by 1.173-MeV and 1.333-MeV gamma photons. Not more than 1% of the total radioactivity is due to
60Co; and not more than 2% of the total radioactivity is due to
58Co,
60Co, and other radionuclidic impurities.
Assay for radioactivity—
Using a suitable counting assembly (see
Selection of a Counting Assembly under
Radioactivity 821), determine the radioactivity, in MBq (µCi) per mL, of Oral Solution by use of a calibrated system as directed under
Radioactivity 821.
