LIQUID SCINTILLATION COUNTING TECHNIQUE: SOME UNUSUAL POSSIBILITIES

Radioactive isotopes emitting either particles or y rays of 1 MeV or X rays of about 30 keV can be measured either in pyrex tubes or in filmware bags placed in classical counting vials containing a liquid scintillator medium. For the tube technique, the counting efficiencies were 14 % for 22Na, 5 % for 125w and 2.5 % for 6'Cu or 65Zn. For the filmware bag technique, they were 22.5 % for 22Na, 12 % for 125i and 4% for 55Zn. Both techniques enabled the measurement of 0.1 to 2 ml of aqueous solutions, and these solutions can be recovered, unchanged, for other purposes. On the other hand, mammalian cells can be grown in the glass tubes, and the incorporated radioactivity can be counted directly. In the case of small-sized radioactive molecules, diluted in a large volume of water (case of dialysates) , it is possible to measure the radioactivity of 10 ml of such solutions, simply by adding 400 mg of PPO (2,5-diphenyl oxazole). After 1/2 hour shaking, the samples prepared in this manner remained stable for about 24 hours. The counting efficien-cies were 25 % for 22Na, 22 % for 6Cu and 2.2 % for 655n and 1251. The results obtained for each of these techniques were reproducible. Further, these techniques are inexpensive, rapid and easy to use