Q: help with scintillation counting

Otter otterpop at pilot.msu.edu
Tue Nov 19 17:04:59 EST 1996

I am doing some basic scintillation counting using tritium.  I checked the
efficiency of the counter using a tritiated machine standard and it came
out to be 64%.  I then counted a sample of tritiated water, which if I used
it as the standard, would give me an efficiency of about 40%.  I then
counted a sample of tritiated toluene, which correlated to a similar
efficiency as the machine standard tritium (64%).  Both the samples (water
and toluene) are 15 years old, but I took into consideration the decay
factor.  Why would I see a difference in efficiency between the tritiated
water sample and the tritiated toluene sample?  Is the water quenching more
which would result in a lower count?  Could there be something such as
evaporation that could have taken place over the last 15 years to the
samples?  I know that the tritiated standard contains toluene.  Could this
have some sort of effect because the tritiated water sample contains no
toluene?  I know all of my calculations are correct and the problem lies
some where between the water and toluene.  Or, maybe the problem might be
that my tritiated water sample could be contaminated or dilluted somehow..

Thanks again for your time and help,


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