A presentation on the stability of carbon-14 labelled compounds

1. Radiochemical Decomposition Carbon-14 labelled compounds Dr Sean L Kitson Almac Isotope Chemistry Laboratories [email_address] 14 C

3. Types of Radiation

7. 14 N 7 + 1 n 0 -> 14 C 6 + 1 H 1

8. Radioisotopes

9. Carbon-14: Martin Kamen 27-FEB-1940 T 1/2 = 5730 Years

11. Classes of Carbon-14 Labelled Compounds

12. Carbon-14 labelled Drugs

13. Carbon-14 Building Blocks

15. Radio-decomposition

20. Specific Activity (SA) of molecules C SA = 62.4 mCi/mmol C C C C C C [1- 14 C] compound SA = 62.4 mCi/mmol C C C C C C [U- 14 C] compound SA= 6 x 62.4 = 374.4 mCi/mmol

21. Decreasing the Specific Activity (SA) Adjusted SA = 62.4/6 = 10.4 mCi/mmol Add 5 equivalents of inactive compound C C C C C C [1- 14 C] compound SA = 62.4 mCi/mmol C C C C C C

22. Modes of Decomposition of Radiochemicals (1960)

25. Carbon-14 Compounds

29. In solution ionization occurs along the tracts of the beta particles in discrete pockets known as SPURS

31. Decomposition in organic solvents

40. Distribution of solute molecules (x) in aqueous and in frozen aqueous solutions – molecular clustering effect on slow freezing

41. Stability of [ 14 C]-Compound 100% 80% 90% Radiochemical purity 4 8 12 20 15 Time (weeks)

42. Effect of Specific Activity Decomposition of [ 14 C]-Compound at 20°C 100% 30% 90% 60% 20 55 120 Specific activities in mCi/mmol 7 Time (days) Radiochemical purity

43. Effect of Temperature Stability of [ 14 C]-Compound 100% 70% 90% 80% -80º -20º 20º 6 3 1 Time (weeks) Radiochemical purity

44. Effect of Free Radical Scavengers Decomposition of [ 14 C]-Compound at 20ºC 100% 90% 80% 70% 4 2 3 1 Time (months) Radiochemical purity + 3% ethanol Aqueous solution

45. ‘ Ideal’ Radioactive Decomposition Rates

46. Screening Solvents: [ 14 C]-Compound