Stability and reproducibility of gel-suspension samples for the liquid scintillation counting of C-14 using N-lauroyl-L-glutamic-alpha,gamma-dibutylamide

Stability and reproducibility of gel-suspension samples were investigated i n order to evaluate the characteristic feature of the gel suspension method for C-14 activity measurement. Commercially available gelling agent, N-lau royl-L-glutamic-alpha,gamma-dibutylamide, was used for the gel-formation of the samples. No change of the counting rate for the gel-suspension sample was observed for more than 2 years after the sample preparation. Four sampl es used for checking the reproducibility of the sample preparation method. The same values were obtained for the counting rate of C-14 activity within the counting error. No change of the counting rate was observed for the "r e-gelated" sample. These results show that the gel-suspension method is app ropriate for the C-14 activity measurement by the liquid scintillation meth od and is useful for a long-term preservation of the sample for repeated me asurement.