Radioassay of Low Specific Activity Tritiated Water by Improved Liquid Scintillation Techniques

THE liquid scintillation technique has achieved considerable popularity as a radioassay method for tritiated water because it combines ease of sample preparation with adequate counting efficiency. However, for low specific activity samples, i.e. samples producing a count approaching that of background, counting times become long and the advantages of the technique become marginal. The purpose of this paper is to describe a method of scintillator sample preparation that increases scintillator performance resulting in a substantial decrease in counting time for low specific activity samples. This is accomplished in two ways: (a) making the water samplescintillating solution ratio optimum, and (b) deoxygenating the scintillating solution. In general, the techniques described here can be applied in the radioassay of water soluble radioisotopes other than tritium.