Tubular-wire dual electrode for detection of thiols and disulfides by capillary electrophoresis/electrochemistry

A new dual-electrode detector for capillary electrophoresis is described. The detector consists of an integrated gold tubular electrode as the generator electrode and a gold wire electrode for detection. The detector configuration, including electrode size and position, has been optimized in terms of detection sensitivity and separation efficiency. After amalgamation of the dual electrode with mercury, the capillary electrophoresis/electrochemistry system was employed for simultaneous detection of thiols and disulfides. The response of cystine was found to be linear from 1 mu M to 1 mM with a LOD of 0.5 mu M (S/N = 3) and sensitivity of 60 pA/mu M. The detection limits represent 200-fold improvement over previously reported dual-electrode designs for the detection of disulfides. The use of this detector for identification of thiol- and disulfide-containing peptides was demonstrated with a tryptic digest of ribonuclease A.