Electrofilament deposition and off-column detection of analytes separated by capillary electrophoresis

Capillary electrophoresis interfaced with electrospray is a convenient tech nique for continuously transferring column effluent from capillary-to-plana r format. Conditions are optimized to produce a narrow (similar to 20 mu m) liquid filament (electrofilament), which is capable of depositing spatiall y focused bands with track widths that are routinely 100 mu m. A fiber opti c-based, laser-induced fluorescence cell is employed to monitor the separat ion on-column while the separated bands are deposited onto a moving substra te. The photodetection of deposited bands is accomplished by using either a charge-coupled device camera or a photomultiplier tube. Deterioration of o n-column separation performance is observed when the electrofilament voltag e is applied. Elevating the inlet of the capillary column, to provide hydro dynamic flow, restores separation performance. Substrate temperature and tr anslational rates are optimized with respect to both off-column separation efficiency and signal intensity, Off-column separation efficiencies of 65 0 00 plates per meter were achieved. A linear dynamic range of 10(3) and a li mit of detection of 10(-8) M were obtained for kiton red deposited onto a r eversed phase thin-layer chromatography plate. To demonstrate the applicabi lity of this technique to more complex separation solutions, a dye mixture was successfully separated and deposited with sodium dodecyl sulfate in the running buffer.