Analysis of Fission Products Using Capillary Electrophoresis with On-Line Radioactivity Detection

Capillary electrophoresis has been used to separate metal ions characteristically associated with nuclear fission. Indirect UV absorbance and on-line radioactivity detection were used simultaneously to monitor the analytes. The radioactivity detector consists of conical plastic scintillating material with the capillary passing through the center to provide a 4π detection geometry. The wide end of the cone is optically coupled to a photomultiplier tube. Transient isotachophoretic techniques were employed to stack large volumes of samples which had low specific activities. Radioactivity detection of ¹⁵²Eu and ¹³⁷Cs was achieved at the nanocurie level for 80−100 nL injections. The detector is approximately 80% efficient, enabling samples resident in the detector window for 0.1 min to be reliably assayed. The separation of ¹³⁷Cs and ^137mBa isotopes, which are in secular equilibrium, was modeled to demonstrate the effects of the rapid decay of ^137mBa.