Counting Carbon Dioxide by LSC
Prior to the introduction of liquid scintillation counting, a primary route of radiotracer analysis was to combust the organic material and detect the 14CO2 so generated in a gas phase proportional counter. Many protocols still call for combustion and 14CO2 counting, and many metabolic studies require quantitation of 14CO2 exhaled by tracer-fed animals. 14CO2 is assayed by trapping it in a liquid phase as a complex with a strong base (carbamate) and then counting the liquid phase.
|Bubbling 14CO2 through carbamate traps the gas in the liquid phase, yielding a suitable sample for liquid scintillation|
This is a single solution containing both carbamate and scintillators. Gas containing 14CO2 is shaken with the cocktail or bubbled through with a sparger. It is advisable to extract the gas with a second volume of solution to ensure capture of >90% of the 14CO2. Cap the vials and count.
In this system, the carbamate is provided as a separate solution, which may enhance capture efficiencies. Shake or bubble the gas with 1ml of OXOSOL 306 and count.
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