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Star Republic: Guide for Biologists

Liquid scintillation counting

1. Add scintillation cocktail to scintillation counter vials.

2. Add your samples to scintillation cocktails in the vials.

3. Also prepare a vial with only scintillation cocktail as control.

4. For counters that count multiple samples, put the vials on the counting rack. Some counters are equipped with the Start tag, and the Stop tag. Mark your first rack with the Start tag and place an empty rack marked with the Stop tag after all your samples.

5. Turn on the counter, select an appropriate program for your isotope. (If program not stored, check user manual on how to setup a program).

6. Press start. Stop when counting is done.

7. Dispose counted vials and scintillation cocktail as hazardous waste.

8. For beta decay, the radioactivity can be calculated from disintegration per minute (dpm). There should be a liner relationship between the counts per minute (cpm) measured by liquid scintillation and dpm.

count per minute (cpm) = disintegration per minute (dpm) * counter efficiency

See Liquid scintillation counter efficiency.

9. To convert between dpm and mCi, use BioToolKit or the following formula:

activity in mCi = disintegration per minute (dpm) / 2,220,000