Postcolumn Radionuclide Detection of Low-Energy β Emitters in Capillary Electrophoresis

A postcolumn radionuclide detection system for capillary electrophoresis (CE) is described. Eluant from an electrophoresis capillary is directed onto a peptide binding membrane that has been previously coated with a solid scintillator. The membrane is moved in a preselected pattern relative to the fixed capillary outlet during electrophoresis. Light emission from scintillation is imaged onto a charge-coupled device (CCD) using a series of 35-mm camera lenses. Detection of two low-energy β^- emitters (³⁵S and ³H) not previously reported for capillary electrophoresis is demonstrated. The separation efficiencies are similar to those obtained with on-line UV detection. The response for ³⁵S-labeled methionine is linear (r² = 0.996) from 66 amol to 11 fmol. Detection limits are 88 zmol (0.03 Bq) for ³²P-labeled analytes, 17 amol (0.94 Bq) for ³⁵S-labeled analytes, and 8 fmol (8.5 Bq) for ³H-labeled analytes.