Carbon Monoxide C 11
(kar' bon mon ox' ide).
» Carbon Monoxide C 11 is a colorless, odorless, non-irritating gas, suitable for administration by inhalation, in which a portion of the molecules are labeled with radioactive 11C. It contains not less than 90.0 percent and not more than 110.0 percent of the labeled amount of 11C expressed in MBq (or in mCi) at the time indicated in the labeling.
Specific activity: dependent upon the amount of radioactivity to be inhaled, but not more than 1.23 mmoles of carbon monoxide per volume.
Packaging and storage Dispense the gas either continuously or batchwise, and preserve in a single-dose container that is adequately shielded. It may also be trapped either on activated charcoal at 196 or on a molecular sieve at 72.
Labeling The label must include the following: the time and date of calibration; the amount of 11C as carbon monoxide expressed as total MBq (mCi) at time of calibration; the expiration time and date; and the statement CautionRadioactive Material. The labeling indicates that in making dosage calculations correction is to be made for radioactive decay, and states that the radioactive half-life of 11C is 20.39 minutes. Each container to hold 11CO shall be independently labeled to indicate lot number and/or batch number. The labeling states that a microbiological filter (0.22 µm) is to be in place to remove any possible particulate matter that could be carried through to the final product.
Radionuclide identification (see Radioactivity 821)
A: Its gamma-ray spectrum is identical to that of a specimen of 11C in that it exhibits a positron annihilation peak at 0.511 MeV and possibly a sum peak of 1.022 MeV, dependent upon geometry and detector efficiency.
B: Radio-gas chromatography using a molecular sieve chromatographic column to determine the absence of [13N]N2 using a suitable radioactivity detector and mass detector.
Radionuclidic purity A multichannel analyzer is used to count all radioactivity from 40 to 2,500 KeV to determine the absence of radiation, other than at 0.511 MeV and 1.022 MeV, over a period of 4 hours. Possible impurities could be 13N2 (t½ = 9.97 min, this gamma ray spectrum is indistinguishable from 11C, (B+) 491 KeV),10C (t½ = 19 sec, 718.3 KeV (100%)), 14O (t½ = 70 sec, 2312.7 KeV (99.4%)). [11C]CO should contain no more than 10% impurities at the time of inhalation.
Radiochemical purity and mass determination [noteThis pharmaceutical may be synthesized by different methods and may therefore contain different impurities. Additional validated tests relevant to the synthetic procedure may be necessary in order to assure radiochemical purity of the final product. ] Confirm by radio-gas chromatography. The gas stream, either directly from the target, or after initial chemical processing, is directed to an injection loop valve of a gas chromatograph and two precalibrated columns, a molecular sieve that allows separation of carbon monoxide from the different air components (O2, N2, and CH4), and a column containing support S3 and of sufficient length to separate CO2 from N2 and CO (which co-elute) and CO2 from NO2 at room temperature. A simple radioactivity detector and a thermal conductivity detector (or equivalent) are required for the mass determination of carbon monoxide. The radiochemical purity is not less than 98%. Mass analysis of the gas-air mixture must demonstrate levels of carbon monoxide less than 1.23 mmoles in the entire dose which is the upper limit for a single-bolus inhalation.
Assay for radioactivity Determine the radioactivity, in MBq (or mCi), by use of a calibrated system as directed under Radioactivity 821.