Counting 14C in High Activity Sodium Carbonate Solution

A P P L I C A T I O N
L S C C O C K TA I L S
LSC in Practice
Counting 14C in High Activity Sodium
Carbonate Solution
Problem
This produces low results since the radioactivity
has been released.
We have seen this problem in the past and had worked
closely with another research laboratory to develop
a procedure that would provide consistent results.
Recommendation
Discussion
Although not immediately obvious, this researcher’s
difficulties are due to improper cocktail selection
for the sample of interest.
Emulsifying cocktails, such as ULTIMA Gold AB,
contain phosphate esters and are buffered to a slightly
acidic pH. The addition of the sodium carbonate
solution to the cocktail results in a reaction between
the slightly acidic phosphate ester and the sample
of interest. Carbon dioxide, a byproduct of this
reaction, is released into the air. Unfortunately, the
radioactive carbon from the sample becomes involved
with the reaction, resulting in the release of 14CO2.
We recommend the use of the following method
to achieve good and reproducible results for high
activity sodium carbonate solutions:
1. Use high performance glass vials (such as
PerkinElmer part number 6001009 or 6001050).
2. Add 10.0 mL Pico-Fluor™ 15 (PerkinElmer part
number 6013059) to a glass vial.
3. Add 1.0 mL water and shake to form a clear
mixture.
4. Add 100 µL sodium carbonate solution and
shake to form a clear mixture.
5. Determine the DPM using a 14C toluene
quench curve.
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007902_19
N O T E
A researcher contacted PerkinElmer to report difficulties in determining the exact DPM of a high activity
sodium carbonate solution. This laboratory was using
PerkinElmer’s ULTIMA Gold™ AB (PerkinElmer part
number 6013309) and had observed unexpectedly
low DPM results which steadily decreased when the
sample was allowed to stand.
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