Detection of radionuclides in capillary electrophoresis using a phosphor-imaging detector

A capillary electrophoresis (CE) postcolumn radionuclide detector has been developed that uses a commercial phosphor-imaging detector and has been optimized for low-energy beta emitters. Eluant from the separation capillary is deposited on a membrane. Emission from radioactive analytes on the membrane is integrated using the phosphor-imaging system for 10-72 h. Results from the phosphor-imaging system are converted to conventional electropherograms. Modifications to a prior postcolumn CE deposition system have been accomplished by adding a buffer makeup capillary; this increases the electrolyte pH range and improves reproducibility. The limit of detection (LOD) for 35S-labeled analytes is 0.13 amol (8.7 pM or 0.007 Bq), while the LOD for 32P-labeled analytes is 4.9 zmol (0.33 pM or 0.002 Bq), with a linear range for 35S-Met from 1.5 amol to 1.5 fmol.