Updated Ph. Eur. 9.4, effective 01/04/2018
Choline ([11C]Methyl) Injection
General Notices
(Ph. Eur. monograph 2462)
11C1C4H14NO+? 103.2?94793-58-5?
Ph Eur
DEFINITION
Sterile solution containing 2-hydroxy-N-[11C]methyl-N,N-dimethylethan-1-aminium ([methyl-11C]choline) ions. It may contain a suitable buffer.
Content
— carbon-11: 90 per cent to 110 per cent of the declared carbon-11 radioactivity at the date and time stated on the label.
CHARACTERS
Appearance
Clear, colourless solution.
Half-life and nature of radiation of carbon-11
See general chapter 5.7. Table of physical characteristics of radionuclides.
IDENTIFICATION
A.?Gamma-ray spectrometry.
Result The principal gamma photons have an energy of 0.511 MeV and, depending on the measurement geometry, a sum peak of 1.022 MeV may be observed.
B.?Approximate half-life: 19.0 min to 21.8 min.
C.?Examine the chromatograms obtained with reference solution (d) in the test for [methyl-11C]choline under Radiochemical purity (see Tests).
Result The principal peak in the radiochromatogram is similar in retention time to the principal positive peak in the chromatogram obtained with the spectrophotometer.
TESTS
pH (2.2.4)
4.5 to 8.5.
Impurity A
Gas chromatography (2.2.28).
Test solution The preparation to be examined.
Reference solution (a) Dissolve 10.0 mg of dimethylaminoethanol R (impurity A) in water R and dilute to 10.0 mL with the same solvent. Dilute 1.0 mL of the solution to V with water R, V being the maximum recommended dose in millilitres.
Reference solution (b) To 0.1 mL of ethanol R add 0.1 mL of acetonitrile R and dilute to 10 mL with water R.
Column:
— material: fused silica;
— size: l = 30 m, ? = 0.32 mm;
— stationary phase: poly[(cyanopropyl)(phenyl)][dimethyl]siloxane R (film thickness 1.8 μm).
Carrier gasnitrogen for chromatography R.
Flow rate 1.5 mL/min.
Split ratio 1:10.
Temperature:
Detection Flame ionisation.
Injection 1.0 μL.
System suitability: reference solution (b):
— resolution: minimum 2.0 between the peaks due to ethanol and acetonitrile.
Calculation of content:
— for impurity A, use the concentration of impurity A in reference solution (a).
Limit:
— impurity A: maximum 1.0 mg/V.
Residual solvents
Limited according to the principles defined in general chapter 5.4. The preparation may be released for use before completion of the test.
Sterility
It complies with the test for sterility prescribed in the monograph Radiopharmaceutical preparations (0125). The preparation may be released for use before completion of the test.
Bacterial endotoxins (2.6.14)
Less than 175/V IU/ mL, V being the maximum recommended dose in millilitres. The preparation may be released for use before completion of the test.
RADIONUCLIDIC PURITY
The preparation may be released for use before completion of test B.
Carbon-11
Minimum 99.9 per cent of the total radioactivity.
A.?Gamma-ray spectrometry.
Limits Peaks in the gamma spectrum corresponding to photons with an energy different from 0.511 MeV or 1.022 MeV represent not more than 0.1 per cent of the total radioactivity.
B.?Gamma-ray spectrometry.
Determine the amount of carbon-11 and radionuclidic impurities with a half-life longer than 20 min. For the detection and quantification of impurities, retain the preparation to be examined for at least 3 h to allow the carbon-11 to decay to a level that permits the detection of impurities.
Result The total radioactivity due to radionuclidic impurities is not more than 0.1 per cent.
RADIOCHEMICAL PURITY
[Methyl-11C]choline
Liquid chromatography (2.2.29).
Test solution The preparation to be examined.
Reference solution (a) Dissolve 5 mg of choline chloride R in water R and dilute to 20 mL with the same solvent.
Reference solution (b) Dissolve 5 mg of fluorocholine chloride R in water R and dilute to 20 mL with the same solvent.
Reference solution (c) Mix 1 mL of reference solution (a) and 1 mL of reference solution (b).
Reference solution (d) Mix 1 mL of the test solution and 1 mL of reference solution (a).
Column:
— size: l = 0.25 m, ? = 4.6 mm;
— stationary phase: cation-exchange resin R2 (5 μm).
Mobile phase Dissolve 20.7 g of sodium dihydrogen phosphate monohydrate R in water for chromatography R and add 80 μL of anhydrous pyridine R. Adjust to pH 2.5 with phosphoric acid R and dilute to 1 L with water for chromatography R.
Flow rate 1.5 mL/min.
Detection Spectrophotometer at 270 nm and radioactivity detector connected in series.
Injection 20 μL of the test solution and reference solutions (c) and (d).
Run time 14 min.
Relative retention With reference to choline: fluorocholine = about 0.9.
System suitability Reference solution (c) using the spectrophotometer:
— resolution: baseline separation between the peaks due to fluorocholine and choline.
Examine the radiochromatogram obtained with the test solution.
Limit:
— [methyl-11C]choline: minimum 95 per cent of the total radioactivity due to carbon-11.
RADIOACTIVITY
Determine the radioactivity using a calibrated instrument.
IMPURITIES
A.?2-(dimethylamino)ethan-1-ol,
B.?iodo[11C]methane.
Ph Eur